Pte. Robert Costall, seen in this undated photo in Afghanistan, was killed after Taliban forces attacked coalition troops north of Kandahar. Forces had been sent to the area after the recent death of eight Afghan army soldiers. ((DND/Canadian Press))

The U.S. army says it haswrapped upa probe into whether a Canadian soldier and a Vermont member of the U.S. National Guard were killed by so-called friendly fire in Afghanistan.

Canadian Pte. Robert Costall, 22,and Tom Stone, 52, an American medic, died during anighttime battle with Taliban insurgents on March 29, 2006.

But the army won't release the results of the investigation until Stone's family is briefed about the findings.

Canada's Department of National Defence is checking to see if Costall's family would also receive a briefing.

The delay in the release of the results was due to the nature of the incident, said Capt. Keith Davio, a spokesman for the National Guard.

"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."

Three other Canadian soldiers were wounded in thebattle that included mortars and rocket-propelled grenades.

At least eight Afghan National Army soldiers were killed, along with as many as 32 insurgents.