MONTPELIER, Vt. — The U.S. army has completed a probe into whether a Vermont National Guardsman and a Canadian soldier were killed by friendly fire in Afghanistan during a fierce night-time battle just over a year ago, a Guard official said Friday.

But the results of the investigation into the March 29, 2006 death of Master Sgt. Tom Stone and Canadian soldier Pte. Robert Costall won't be released until Stone's family has been briefed about the findings, said Guard spokesman Capt. Keith Davio.

A spokeswoman for the Canadian Defence Department was checking Friday to see if a similar briefing would be given to Costall's family.

The delay in the release of the results was due to the nature of the incident, Davio said.

"The biggest thing is it involves the three different governments," the U.S., Canada and Afghanistan, said Davio. "Specifically what took so long, we don't know that yet."

Stone and Costall died during the firefight that followed a Taliban attack on a base in a remote part of southern Afghanistan. The attack that was repelled by U.S., Canadian and Afghan soldiers.

A week later, the Vermont National Guard announced that a friendly fire investigation was under way to determine if Stone and Costall were killed by their allies.

The possibility that Costall, a 22-year-old machine gunner, died as a result of friendly fire was raised by his wounded buddies when the multinational brigade commander, Canadian Brig.-Gen. David Fraser, visited them in hospital.

The troops told Fraser they had been hit by fire from their own side as they rushed to take up position in one corner of the arid, hilltop base overlooking the village of Sangin.

Costal, who was born in Thunder Bay, Ont., and grew up in Gibsons, B.C., was part of a quick-reaction force that was rushed to the outpost, which was in danger of being overrun by insurgents and militias belonging to local drug lords.

Aside from Costall and Stone, three other Canadian soldiers were wounded in the firefight. At least eight Afghan National Army soldiers were killed, along with as many as 32 insurgents.

Stone's longtime companion, Rose Loving of Tunbridge, has said she was told by U.S. soldiers who were there that Stone was killed by friendly fire. She says she's frustrated because the army wasn't being forthcoming about its investigation.

She has been working with U.S. Sen. Patrick Leahy to get the army to finish the investigation and release the results.

In January and again last month, Leahy, (D.Vt.), wrote to the Secretary of the army asking him to tell Stone's family what happened. In the second letter, Leahy said the army's handling of the situation seemed insensitive.

"We owe our service personnel support when we send them into harm's way," he said in a statement Friday. "But, we also owe support to them when they come home, and to their families when they don't come back. I'm disappointed with how this has been handled by the army."

Loving said she expected to be briefed later this month.

"This is the first real information we have heard in over a year," she said in an e-mail message.

Stone, 52, of Tunbridge, joined the army after graduating from high school in 1971, in part to try to learn what happened to his older brother, a freelance photographer who disappeared in Cambodia in 1970 along with Sean Flynn, the son of actor Errol Flynn.

The two were never seen again and are believed to have been killed by communist guerrillas.

Stone was in and out of the military several times over the years and in the interim spent eight years walking around the world. He was on his third tour in Iraq when he was killed.