Commodore Dan Murphy said a major fire had spread through the commanding officer's cabin on the second deck of the HMCS Chicoutimi, while a smaller blaze started in an oxygen generator about 50 feet (15 meters) away.
``It was startling for all of us,'' Murphy told a news conference. ``This was a major fire. There were, in fact, two fires, one of a lesser degree, and three locations were involved.''
``We don't know the relationship at this point. But it was clear to me there were two separate fires, possibly from separate sources. It was clear one fire was major and the other, by appearances, was not,'' he said.
One crew member died and two others were injured as a result of the fire that crippled the diesel-powered submarine last week, three days after it left Scotland for Canada.
The vessel was adrift in rough seas some 160 kilometers (100 miles) northwest of Ireland until British vessels towed it back to the Scottish naval base of Faslane on Sunday.
Murphy is heading a five-member inquiry board which plans to set out in detail the sequence of events aboard the Chicoutimi, which Canada had bought from Britain.
He said the ship's commanding officer, Luc Pelletier, had turned over papers including sailing and technical orders, the sub's log and a list of crew members on watch.
``The work of the board has started to sift through that initial documentary evidence,'' Murphy said.
``Make no mistake - this is an inquiry and investigation to uncover the facts, and recommendations following out of conclusions that are based on fact,'' he said. ``It's not about blame.''
Murphy hopes to present the results of his report Nov. 30 in Ottawa.
Lt. Chris Saunders, 32, died after being airlifted off the Chicoutimi to Sligo General Hospital in Ireland.
A hospital spokeswoman said Tuesday that one of Saunders' injured shipmates, Petty Officer Denis Lafleur, had been discharged, and the other, Master Seaman Archibald MacMaster, was expected to leave the hospital within a few days.