Large pieces of the wreckage of an Air-India Boeing 747 that crashed into the Atlantic nearly two weeks ago have been located on the ocean floor under 6,700 feet of water, it was announced today.

Spokesmen for the British company Cable and Wireless said that its unmanned submarine had located 10 large pieces of wreckage laid out in a line about four miles long. The pieces included portions of the jumbo jet's cabin as well as seats and pieces of the tail. Canadian officials participating in the search said tonight that searchers believed that they had "localized" the plane's "black box" flight recorders based on signals and television pictures.

Boeing 747s carry two flight recorders, one for information from the aircraft's instruments, the other for sounds in the cockpit. Investigators hope recovery of the black boxes will explain why the plane crashed, killing all 329 passengers and crew aboard.

The Toronto-Bombay flight had made a stop in Montreal and crashed off the Irish coast June 23, less than an hour before it was scheduled to land at London's Heathrow Airport for refueling. Air traffic controllers monitoring it by radar in Ireland said the pilot issued no distress call, and the plane simply vanished from their radar screens.

Indian government officials and aviation experts here have said they suspect from the circumstances of the crash that a bomb may have been on board. The leader of an Indian government investigative team said yesterday that examination of wreckage found floating and autopsies on the 131 bodies that were recovered from the sea in the first two days after the crash suggested that the plane had exploded in midair.

Three ships are operating in the vicinity of the crash. One, a French cable-laying ship chartered by the Indian government, is looking only for wreckage. The Cable and Wireless submarine is tethered to this ship.

Sonar aboard the ship first located pieces of wreckage, and the submarine then was submerged to photograph the pieces with television cameras. It is not yet certain whether an effort will be made to bring the pieces of wreckage to the surface. The submarine is operating at the far end of its depth capabilities and is attached to the French ship via the world's longest remote control cable, flown here by the Canadian government.

The other two ships, an Irish naval vessel and a British survey ship, the Gardline Locater, chartered by Britain on behalf of the Indian government, are cruising the area trailing hydrophones that are equipped to pick up radio signals from the flight recorders.

As the search goes on for evidence that could prove conclusively what happened to Air-India Flight 182, one part of the investigation is drawing to a close. Canadian and Indian government officials as of today have identified 103 of the 131 bodies recovered from the crash.

A Canadian official reached by telephone at the search and investigation headquarters in Cork, Ireland, said that about 230 relatives of 221 of the crash victims had traveled from Canada to try to identify the victims. Most of the passengers were Canadian citizens of Indian origin.

Other relatives have traveled from India. With just more than one-third of the bodies recovered, however, many relatives have had to return home without having made a positive identification.

All of the relatives, whose expenses were paid by Air-India, have been asked to bring medical and dental records as well as photographs of the passengers. Families go through a four-hour interview with Irish police officers in charge of the identification and then are taken into a room where facial photographs of the bodies are displayed.

Those who make a reasonably certain identification from a photograph then are taken to see the body for final identification.