SANTIAGO, Chile (AP) _ Passengers clung desperately to the wings and tail of a sinking Chilean jetliner that skidded off a runway into icy waters near Cape Horn, witnesses said today. Authorities said 20 died and 17 were injured.

One Texas survivor of Wednesday's crash described a frantic struggle to get out of the plane as water rushed in and drowned her husband and others inside, a relative said.

Investigators were probing what caused the chartered jet, with 65 mostly American passengers on their way to an Antarctic cruise, to overshoot the runway while trying to land at Puerto Williams during a light rain.

The British-made BAe-146, a small four-engine jet, crashed into Beagle Channel off Navarino Island, about 1,500 miles south of Santiago and 60 miles north of Cape Horn, said the Chilean airline LAN.

A U.S. diplomat, Lawrence Kerr, flew to Puerto Williams early today with an investigative group led by Chilean air force Cmdr. Hernan Barahona.

The Chilean navy said 20 passengers died, while the airline said 19 were killed. A list of the victims was not expected until later today. The seven crew members survived.

LAN said 17 people were ''slightly injured'' and were being treated at the a navy hospital in Puerto Williams.

But Chilean press reports today said two of the injured were in serious condition, including an elderly American woman who suffered a heart attack. LAN did not immediately comment on the reports.

Passengers grabbed onto the plane's wings and tail and waited for rescuers, while others tried to swim to the beach 150 yards away, reporters said.

''The aircraft started to sink, while the passengers emerged, many of them clinging to the wings, awaiting to be rescued,'' reported Maria Cristina del Pino, a correspondent for the Santiago daily El Mercurio in Puerto Williams.

''After 10 minutes, all you could see was the tail,'' she said.

Navy personnel using rubber boats quickly reached the scene, she added.

Islanders including many fishermen cooperated in the rescue with their small boats, said Mauricio Carvajal, who works at Puerto William's radio station.

''Several passengers, in despair, jumped into the water trying to swim to the beach,'' he said. ''We who live here would never dare to do that. The water is like ice, and you may freeze and die in a matter of minutes.''

Julie Brice Lally, 31, of Dallas said her 28-year-old husband, Garvin Lally, was unable to swim free, according to her father, Bill Brice Sr.

''Several people got off ahead of them, but before they could get off the plane filled up with water and some of the passengers drowned,'' Brice said in Dallas. ''She thought she was going to drown about three times.''

Brice said his daugher was not injured.

The plane had flown to Puerto Williams from Punta Arenas, 300 miles to the north, where the passengers had arrived on a commercial flight from Santiago.

The passengers were to begin an Antarctic vacation cruise from Puerto Williams organized by Seattle-based Society Expeditions, Peter Cox, company planning director said in Seattle.

An official with the Atlanta-based Cecil Day Investment Co. said three of the dead were members of a 12-person group of company employees, relatives and friends. The names of the victims were not released.

Survivors included Deen Day Smith, a member of the Georgia University Board of Regents and the widow of Cecil Day, founder of the Days Inn motel chain, said Furman H. Agee III, the company's executive vice president.

Among the survivors were the crew - two pilots, four flight attendants and a mechanic, said LAN President Jose Luis Moure.

Thirty other tourists also part of the Society Expeditions trip had landed safely in Puerto Williams earlier Wednesday on a flight from Punta Arenas, Cox said.

The vacationers had arrived in Santiago from Miami on Tuesday and traveled together to Punta Arenas on a commercial flight, he said.

The tourists planned to board the ship Society Explorer in Puerto Williams to be ferried to Antarctica, said Miguel Rivero, manager of the travel agency that handled the plane charter. The nearest Antarctic point is about 1,000 miles south of Puerto Williams.