The salvage team recovering pieces of the Air India Boeing 747 that crashed into the North Atlantic in June has found 13 holes in one section of a baggage compartment wall, possibly the first solid evidence that a bomb felled the airliner and caused the death of its 329 occupants.

U.S. officials said that the discovery is not definitive and that the Canadian salvage vessel Kreuzturm will try for another 10 days to recover more pieces.

"The things that were described by the metallurgist and the structures guy on the ship definitely require a closer look," a U.S. source said, "but it wasn't enough to stop the salvage operation and run back to the shore."

Details are few, due to limited radio communication and the absence of laboratory facilities on board. The on-board experts are from the Indian government, which is heading the investigation, and the Boeing Co., which manufactured the airplane.

Investigators, studying extensive underwater photographs of the wreckage, developed a priority list of 30 pieces they wish to examine closely. By yesterday, five pieces had been brought to the surface from a depth of about 6,600 feet. When salvage is completed, the recovered pieces will be taken to Dublin, Ireland, for analysis.

The holes were found in the third piece recovered, a 10-by-12-foot section of fuselage skin from the forward cargo hold, under the first-class section near the cockpit, where baggage is stowed.

"We don't know the size or shape of the holes," National Transportation Safety Board spokesman Ira Furman said. "They have been described to us as penetrations. What investigators want to do is confirm that the punctures are in an outward direction."

Penetrations from inside would lend credence to the bomb theory. Laboratory analysis can determine the speed with which the skin was penetrated and might detect the presence of explosives.

Callers to U.S. newspapers claiming to represent two Sikh extremist groups, the Sikh Student Federation and the Kashmir Liberation Front, have claimed responsibility for the crash.

Boeing, the Federal Aviation Administration and Air India hope that bombing will be established as the cause, because that would rule out any structural defect or damage that should have been caught in manufacture, certification or maintenance.

The Indian government is of a like mind. The claims by the Sikh separatist groups appear to isolate the extreme wing of that movement, according to reports from New Delhi. Most Sikh leaders in India and abroad have condemned what has been assumed from the beginning to be a terrorist attack.

Sikh leader Jagjit Singh Chauhan, who applauded the assassination of prime minister Indira Gandhi last October by Sikh bodyguards, and Joginder Singh, father of an extremist leader killed in June when the Indian army stormed the Golden Temple, the holiest Sikh shrine, have joined the condemnations.

The Canadian government, which has participated extensively in the investigation, "is going to be unhappy if this turns out to be a bomb, because that means Canadian security failed," one U.S. official said. The flight originated in Toronto, and more passengers boarded in Montreal. Luggage was checked at both locations.

Harry Boyko, who heads the Canadian investigating team, told Reuter yesterday, "We may have a piece with holes in it, but it doesn't prove they were caused by a bomb."

An hour before the Air India crash, an explosion at Tokyo's Narita International Airport killed two baggage handlers unloading a flight from Vancouver, British Columbia. Canadian and Indian investigators have assumed that the two incidents were related.

Enormous liability suits have been or will be filed, and who pays the settlements will depend on whether a bomb is to blame.