A coalition helicopter trying to supply Afghan police with munitions dropped them in the wrong location and Taliban fighters later recovered the weaponry, an Afghan intelligence official said.
A member of parliament, however, said he did not believe the arms drop was an accident.
Amrullah Saleh, the head of Afghanistan's intelligence service, told a parliament security committee that "coalition forces" intended to place weapons, ammunition and food at a police checkpoint in a remote section of the southern province of Zabul in late March.
"By mistake it was dropped somewhere far from the checkpoint. Later the Taliban came and they picked it up," Saleh told reporters after addressing the committee.
In his testimony, he said a "small box" had been dropped but did not say how many weapons were inside.
It was not clear whose helicopter left the supplies.
Maj. Richelle Dowdell, a spokeswoman for NATO's International Security Assistance Force, said the helicopter involved was not NATO's. Lt. Richard Ulsh, a spokesman at the U.S. base at Bagram, said the U.S.-led coalition was not involved either.
Hamidullah Tukhi, a lawmaker from Zabul, told the security commission the weapons were placed 300 feet from the home of a Taliban commander named Mullah Mohammad Alam. He said the supply drop contained heavy machine guns, AK-47s, rockets and food.
Lawmakers discussed the issue with President Hamid Karzai and U.S. Gen. Dan McNeill, the top NATO commander in Afghanistan, he said.
"I think Gen. McNeill himself said that it was a mistake, but I don't believe it," Tukhi said, adding he did not know which nation dropped the supplies.
Saleh told journalists Tukhi's version of events was based on "rumors."