A Canadian board of inquiry began its investigation Monday into the U.S. friendly fire incident that killed four Canadian soldiers in Afghanistan.

Eight soldiers were also injured when an American F-16 pilot on a night patrol apparently mistook the Canadians for enemy forces. The pilot thought he was acting in self-defense when he dropped a 500-pound bomb on them in the early morning hours Thursday, U.S. officials have said.

The Canadians were conducting a live-fire training exercise near the southern Afghan city of Kandahar.

The five-member inquiry board, headed by former defense chief Maurice Baril, a retired general, is scheduled to file an interim report with Defense Minister Art Eggleton within three weeks. The final report is expected within 60 days.

Eggleton said he expects the board to travel to Afghanistan soon.

"We've asked them to find out what happened as quickly as they can," Eggleton said.

A separate U.S. military investigation is also being conducted, and Defense Secretary Donald H. Rumsfeld promised full cooperation with Canada.

"Whatever is done will be transparent to the Canadians," Rumsfeld said.

Asked whether access to the U.S. pilot will be granted, Rumsfeld replied: "The Canadian armed services will have observers present in every aspect of it. ... They are conducting a parallel but separate investigation of their own."

Canada's inquiry board will include Canadian Brig. Gen. Marc Dumais, who will also sit on the U.S. panel of investigators.

Eggleton said Dumais will be able to question anyone brought before the U.S. investigators. "All of the information that we want will be provided," Eggleton said.

The investigators are expected to determine why the pilot did not know the Canadians were there. All allied troops operating in the Kandahar area are supposed to be aware of friendly forces.

President Bush telephoned Canadian Prime Minister Jean Chretien immediately after the accident. But he touched a nerve in the Canadian press when he made no public comment about the accident Thursday except for a written statement released late in the afternoon.

Friday morning editions of the Toronto Globe and Mail carried a headline that read, "Deaths don't merit a mention from Bush; U.S. indifference."

On Friday, Bush pledged: "We'll find out what happened. It was a terrible accident."