NEW DELHI, India (AP) _ A report by Canadian investigators concludes that a bomb exploded in the cargo hold of an Air-India Boeing 747 off the Irish coast last June and caused it to crash, killing 329 people, a Canadian official said Wednesday.

Canadian investigator Bernard Caiger confirmed the previously undisclosed report and its conclusions, prepared by Canadian Aviation Safety Board, in testimony before the Indian High Court.

The court is conducting the official government inquiry into the June 23 disaster that killed all aboard the jetliner, most of them Canadians of Indian descent. The report, which Caiger called a ''draft,'' has not been entered into evidence.

Under cross-examination by Steve Bell, a lawyer representing the Seattle- based Boeing Aircraft Corp., maker of the airplane, Caiger said he had only ''briefly'' seen the report. He refused to name the investigators who prepared it.

Pressed repeatedly by Bell, Caiger finally confirmed the report's conclusions.

''I'm not sure whether it says a bomb was the cause or a probable cause,'' Caiger said. He added later: ''I don't believe the report mentions any other cause.''

Indian investigators have theorized that Sikh extremists angry with the Indian government planted a bomb aboard the India-bound plane before it left Canada. The jet, flying from Toronto and Montreal, was heading for a refueling stop in London when it plunged into the North Atlantic.

Caiger also testified that his study of the jetliner's cockpit voice recorder found a ''bang'' just before something cut the microphone lines to the recorders and less than 1.5 seconds before electrical failure terminated the recording.

But Caiger, an expert in cockpit voice and flight data recorders, said he couldn't be sure the ''bang'' was caused by an explosion.

Lawyers for other parties appearing before the inquiry said they had not heard of the Canadian report before Wednesday. Ivan Whitehall, attorney for the Canadian government, said it would be given to the inquiry after the drafters review new evidence.

In Ottawa, the Canadian board's chief of safety investigations, Tom Hinton, refused to confirm the crash was caused by a bomb or give other details of the board's analysis. He said there could be last-minute changes to the report before it is presented to the inquiry.

Under international law, India has jurisdiction for the official inquiry because the disaster occurred in international airspace and involved an Indian-registered aircraft.

The Canadian board's conclusions support the findings of Indian scientists who studied fragments of the jetliner recovered from the seabed about 115 miles off the Irish coast.

The scientists, expected to testify about their conclusions later this week, found ''unique'' blast damage in the recovered remains of the jet's forward cargo hold.