The suicide bomber who killed seven CIA employees at a remote outpost in southeastern Afghanistan had been invited onto the base and had not been searched, two former U.S. officials told The Associated Press on Thursday.
A former senior intelligence official says the man was being courted as an informant and that it was the first time he had been brought inside the camp. An experienced CIA debriefer came from Kabul for the meeting, suggesting that the purpose was to gain intelligence, the official said.
The former intelligence official and another former official with knowledge of the attack spoke on condition of anonymity because they were not authorized to speak publicly.
The CIA would not confirm the details, and said it was still gathering evidence on the incident.
"It's far too early to draw conclusions about something that happened just yesterday," said spokesman George Little.
Blow to tight-knit spy agency
A separate U.S. official suggested the bomber may have set off the explosives as he was about to be searched.
The bombing on Wednesday dealt a blow to the tight-knit spy agency. Among those killed was the chief of the CIA post, whom former officials identified as a mother of three. Six more agency personnel were wounded in what was considered the most lethal attack for the CIA since the war in Afghanistan began in 2001 and possibly even since the 1983 embassy bombing in Beirut.
It also was the single deadliest attack for Americans in Afghanistan since eight soldiers were killed in an insurgent attack on a base in the east on Oct. 3.
President Barack Obama and CIA Director Leon Panetta were joined by several leading lawmakers on Thursday in praising agency employees for their work.
"Those who fell yesterday were far from home and close to the enemy, doing the hard work that must be done to protect our country from terrorism," Panetta said in a statement confirming the deaths. "We owe them our deepest gratitude, and we pledge to them and their families that we will never cease fighting for the cause to which they dedicated their lives -- a safer America."
In a letter to CIA employees, Obama said their fallen colleagues came from a "long line of patriots" who had helped to keep the nation safe despite grave risks.
Obama acknowledged that the spy agency has been tested "as never before" since the attacks of Sept. 11, 2001.
The CIA did not release information about the victims, citing the sensitivity of their mission and other ongoing operations. Harold E. Brown Jr., a State Department employee of Fairfax, Va., died in the attack, his father, Harold E. Brown Sr., told The Associated Press on Thursday.
The younger Brown, 37, who grew up in Bolton, Mass., served in the Army and remained a major in the reserves. He is survived by a wife and three children ages 12, 10 and 2.
Deep bench in Afghanistan
According to one former agency employee, the death toll represents a significant portion of the CIA's clandestine force in the region, but that many of the agency's employees have experience in Afghanistan.
"The bench is deeper in Afghanistan than it is anywhere in the world," the former employee said.
The bigger question for CIA operations will probably be whether the agency moves to tighten safety rules for its employees, the former employee said.
The incident occurred at a former military base on the edge of Khost city, the capital of Khost province which borders Pakistan and is a Taliban stronghold.
The Taliban claimed responsibility.
Taliban spokesman Zabiullah Mujahid said in a statement that an Afghan National Army officer wearing a suicide vest entered the base and blew himself up inside the gym. A U.S. official briefed on the blast also said it took place in the gym.
Forward Operating Base Chapman used to be a military facility base but was later turned into a CIA base, according to a U.S. official, who spoke on condition of anonymity because he was not authorized to speak publicly.
Other deaths of CIA operatives
Only four known CIA operatives have been killed in Afghanistan since the 9/11 terrorist attacks in the U.S.
CIA officer Micheal "Mike" Spann was killed in a prison uprising in November 2001. An agency officer died in a training exercise in 2003, and two contractors operating out of a CIA base in Shkin district of Paktika province were killed the same year.
The attack came on a bloody day for NATO forces. A roadside bombing, also claimed by the Taliban, killed four Canadian troops and a Canadian journalist in southern Afghanistan. Elsewhere, police said militants beheaded six Afghans on Thursday for cooperating with government authorities.
Michelle Lang, a 34-year-old health reporter with the Calgary Herald, was the first Canadian journalist to die in Afghanistan. She arrived in the country just two weeks ago. Lang "was one of those journalists who always wanted to get to the bottom of every story so this was an important trip for her," said a Calgary Herald colleague, Colette Derworiz.
The military has not disclosed the names of the Canadian troops because relatives have not all been notified.
Community security patrol
Brig. Gen. Daniel Menard, commander of coalition forces in Kandahar, said the soldiers were conducting a community security patrol.
According to figures compiled by The Associated Press, 32 Canadian troops have been killed in Afghanistan this year; in all, 138 have died in the war.
Afghan President Hamid Karzai issued a statement of condolence to Americans and Canadians, saying "your children sacrificed their lives for the people of Afghanistan and the threat of terrorism. The Afghans will not forget your sacrifice."
Karzai has been critical of NATO forces, though, for attacks that have killed civilians. Claims of civilians killed by foreign forces are a highly emotional issue among Afghans and feed strong resentment of international soldiers.
Top NATO commander Stanley McChrystal has made avoiding such deaths a critical part of his strategy.
The attack last weekend in Kunar province has been a bone of contention between the Afghan government, which said 10 civilians were killed, and NATO, which said there was no evidence to substantiate that claim.
On Thursday, U.N. special representative in Afghanistan Kai Eide said in a statement that although insurgents were in the area at the time, eight of the 10 killed in the nighttime attack were students in local schools.
Separately, a spokesman for the governor of Helmand province in the south said an airstrike by international forces killed and wounded civilians. Dawud Ahmadi said he did not know how many were killed Wednesday in Babajid district. He said the attack took place after an international forces patrol came under fire.