The main ingredient in most of the homemade bombs that have killed hundreds of American troops in Afghanistan is fertilizer produced by a single company in Pakistan, where the U.S. has been pushing unsuccessfully for greater regulation.
Enough calcium ammonium nitrate fertilizer for at least 140,000 bombs was legally produced last year by Pakarab Fertilizers Ltd., then smuggled by militants and their suppliers across the porous border into southern and eastern Afghanistan, according to U.S. officials.
The U.S. military says around 80 percent of Afghan bombs are made with the fertilizer, which becomes a powerful explosive when mixed with fuel oil. The rest are made from military-grade munitions like mines or shells.
The United States began talks a year and a half ago with Pakistani officials and Pakarab, one of the country's largest companies. But there is still no regulation of distribution and sale of calcium ammonium nitrate fertilizer.
"If you have a host country that has a factory making a substance that ultimately becomes the problem, then that country has to contribute at least half the solution," said Democratic Sen. Bob Casey of Pennsylvania, who led a congressional delegation to Pakistan last week to press army and civilian leaders for action.
U.S. officials say Pakistan and Pakarab have expressed willingness to regulate the fertilizer, which is also widely used in the manufacture of bombs used by insurgents to kill thousands of soldiers and civilians inside Pakistan. They acknowledge the difficulties: 15 years after ammonium nitrate was used in the Oklahoma City bombings, the U.S. government only presented its proposals to regulate it on Aug. 2.
But with the death toll from homemade bombs rising almost daily inside Afghanistan, continuing inaction by Pakistani authorities will add more strain to a U.S.-Pakistani relationship already frayed by allegations that Islamabad is aiding Afghan insurgents on its side of the border.
"This is a test," Casey said. "The key thing now is to see results."
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The only producer of calcium ammonium nitrate fertilizer in Pakistan, Pakarab operates two factories in Punjab province, the country's agricultural heartland.
The largest is on the outskirts of Multan, an ancient city surrounded by thousands of acres (hectares) of mango orchards and cotton fields. A sprawling industrial complex of smoking chimneys, pipes and tanks surrounded by high walls, the 39-year-old facility churns out the chemical 24 hours a day when it's operating.
Lines of trucks wait outside to transport sacks of fertilizer to 2,000 distributors around the country, who then sell it to millions of Pakistani cotton, fruit and wheat farmers.
Around Multan, dealers sit in small shops in front of piled-up sacks of ammonium nitrate and other fertilizer, haggling with farmers. Most say they are aware ammonium nitrate can be used as an explosive, but none has been told to report suspicious purchases.
Pakistani fertilizer producers are not permitted to export to Afghanistan because they are subsidized by the government and their products are meant for domestic use only. But the low price of fertilizer in Pakistan, and a chronic shortage in Afghanistan, has meant that smuggling has long been rife.
The chemical, known as CAN, is often trucked into southern Afghanistan repackaged as a harmless fertilizer. Other times, it's hidden under other goods, often after border guards have been paid a bribe, according to smugglers at the Chaman border and U.S. officials.
One dealer, Mohammad Wassem, told The Associated Press wealthy people with links to the insurgents placed orders for all three fertilizers produced by Pakarab. They sold the two safer varieties domestically, then trucked the ammonium nitrate across the border.
Truck driver Ali Jan said he makes $20 each time he crosses the border with concealed sacks of fertilizer.
"I do not take banned items every time, but I make at least 10 trips a month across the border carrying bags of fertilizer under other stuff," Jan said.
Only a tiny fraction of the trucks that cross the border are searched, said one U.S. official, explaining it would be impractical to stop and search the many thousands of vehicles that cross the border each day.
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Explosives can be made from a range of fertilizers, but it is easy to turn CAN into a bomb. Insurgents either grind or boil the small, off-white granules to separate the calcium from the nitrate, which is mixed with fuel oil, packed into a jug or box and then detonated.
The fertilizer is sold in 110-pound (50-kilogram) sacks, which can be used to make between two and four bombs depending on whether they are targeting vehicles or foot patrols, said Robin Best, an expert at the U.S. military's Joint IED Defeat Organization, who visited the Multan factory in July with a U.S. delegation.
Such bombs, typically buried and detonated remotely or by pressure plates, have killed more than 719 Americans and wounded more than 7,440 since the conflict began in 2001, along with thousands of Afghan troops and civilians. Last year's U.S. death toll — 252 — was as high as the two previous years combined, and 2011 is shaping up to be just as bloody.
Based on tests of residues at a limited number of blast sites, and seizures of the chemical inside Afghanistan, two U.S. officials told the AP they believe the majority of fertilizer bombs in Afghanistan are made of CAN produced by Pakarab. One said that up to 80 percent of the bombs were made with Pakarab fertilizer. Both asked for anonymity because of the sensitivity of the data.
Casey, the senator from Pennsylvania, said the U.S. government estimates around 1 percent of Pakarab's annual production made it ways across the border for use in bombmaking. Given that the company produced 350,000 metric tons in 2010, that means enough for at least 140,000 bombs was smuggled across the frontier last year, though an unknown amount was seized by Afghan and U.S. authorities, or stockpiled.
On Aug. 17, authorities in Afghanistan's Helmand province said they seized 200 sacks of ammonium nitrate that had been smuggled from Pakistan. Photos of the sacks, which had been partially buried, showed they were made by Pakarab.
"All of this chemical is coming from the south and the east," said Mohammad Zahir Azimi, a spokesman for the Afghan Defense Ministry. "We want Pakistan to control it."
Executives of Pakarab, a publicly traded company, defended their right to sell what is a legal product well-suited to the soil and weather in Pakistan. They said the company had no way to dispute U.S. and Afghan claims about where its fertilizer is ending up, but noted ammonium nitrate was produced in other countries around the region and that Pakistan also imported it.
"Pakarab will continue to work with both the (U.S. and Pakistani) governments unreservedly," the company said in a statement.
The company added that Washington had provided assurances it had no plans to press for the plants to be closed.
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Most countries have placed restrictions on the sale, purchase and storage of the chemical, and some, including Germany, Afghanistan, Ireland and China, have banned it. Some U.S. states already regulate it, but new federal proposals would require those who purchase and sell it to register with the government and limit its movement across states.
The U.S. is discussing similar kinds of regulations in Pakistan, but acknowledges that enforcement will be difficult in a country where police and government officials are underpaid, lack education and are facing numerous other challenges.
Still, there are signs that Pakistan may not fully understand the problem or lack the ability to address it.
After a meeting with Sen. Casey, Prime Minister Yousuf Raza Gilani issued a statement saying the government had already introduced "strict laws" regulating the product, implying that nothing further needed to be done. An army spokesman even maintained there were no longer any factories producing calcium ammonium nitrate in Pakistan, before being corrected by the AP.
"I don't think the magnitude of the problem has been understood," said a U.S. official, who asked not to be named to discuss the issue frankly. "There hasn't been a comprehensive look (by Pakistan) at it. We are having frank discussions. We are taking that as progress."
Casey said he hoped new regulations to control the product could be in place as soon as the end of the fall.
The U.S. has also been trying to get Pakarab to switch to producing a version of the fertilizer that's more difficult to turn into bombs — something scientists have been trying to accomplish since the use of nitrate fertilizers was pioneered by Irish Republican militants in the 1980s.
Last year, executives with the U.S. chemical manufacturer Honeywell traveled to Pakistan to pitch Pakarab on the merits of Sulf-N 26, a fertilizer that combines ammonium nitrate with ammonium sulfate, a fertilizer and fire retardant.
Honeywell unveiled Sulf-N 26 in 2008 in response to security concerns after the Oklahoma City bombing, and bills it as safe as sand when mixed with fuel.
However, tests carried out in the U.S. showed it could still be used in the production of bombs and the project was shelved, according to Pakarab and Best, the expert at the Joint IED Defeat Organization. Honeywell, which said it had not been informed about the tests, disputed that conclusion.
Pakarab is now testing the feasibility of dyeing CAN to distinguish it from other harmless fertilizers at the border.
Such a process has never been tried before. Pakarab said the dyeing initiative was "encouraging."
"The dye is a huge thing. It's the first step that could have a profound impact," Best said.
One concern is whether farmers, most of whom are illiterate and resistant to change, would buy the dyed product, Best said. He said Pakarab was planning a marketing campaign to inform them that its quality remained the same, or possibly better, with the addition of extra chemicals.
While calcium ammonium nitrate accounts for just 10 percent of fertilizer sales across Pakistan, it accounts for most of the fertilizer produced by Pakarab. The company's sales of CAN grew by 20 percent in 2010 from a year earlier, and the company continues to aggressively market it.
Pakarab made $104 million in profit last year, and has hired BNY Mellon to help it become the first Pakistan-based company to sell shares on U.S. stock markets.
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Associated Press Writers Deb Riechmann in Kabul and Matiullah Acakzai in Chaman contributed to this report.