OXNARD, Calif. (AP) _ An Alaska Airlines jet carrying 65 passengers and five crew members from Mexico to San Francisco crashed Monday in the Pacific Ocean after reporting mechanical difficulties.

Flight 261 from Puerto Vallarta was reported down 20 miles northwest of the Los Angeles airport about 3:45 p.m., the Federal Aviation Administration said. Pieces of wreckage could be seen in the water, but there was no sign of survivors.

A Coast Guard helicopter, a Navy airplane and small boats were searching a large field of debris rolling in swells off Point Mugu as darkness began to descend on the ocean. Spotlights illuminated the water, which typically has a temperature in the low 50s this time of year.

``Right now they are searching for survivors,'' said Coast Guard Lt. Jeanne Reincke. ``They see a large debris field, but that's all we've heard from them.''

The jet's crew had reported mechanical difficulties and asked to land at Los Angeles, said Ron Wilson, a spokesman for the San Francisco airport. The flight was scheduled to continue to Seattle after San Francisco.

``Radar indicates it fell from 17,000 feet and then was lost from radar,'' Wilson told KRON-TV in San Francisco.

FAA spokesman Mitch Barker said the plane was a Boeing 737. Boeing spokeman Craig Martin said the company was told by Alaska Airlines that the plane was an MD-80.

Cynthia Emery, FAA flight operations officer in Seattle, confirmed the number of passengers and crew.

On Sunday, a Kenya Airways flight crashed into the Atlantic Ocean shortly after take off from Abidjan, Ivory Coast. The Airbus 310 carried 10 crew members and 169 passengers. At least 10 people survived.

Last Oct. 31, EgyptAir Flight 990 plummeted into the ocean 60 miles south of the Massachusetts island of Nantucket. All 217 people aboard the Boeing 767 were killed.

Alaska Airlines, which has a distinctive image of an Eskimo painted on the tails of its planes, has an excellent safety record. It has built itself into a western power by serving more than 40 cities in Alaska, Canada, Mexico and five Western states. Its headquarters are in Seattle.

The airline had two fatal accidents in the 1970s, both in Alaska, according to Airsafe.com, a Web site that tracks plane crashes.

In 1971, an Alaska Airlines Boeing 727 approaching Juneau crashed into a mountain slope after the crew had received misleading navigational information. All 104 passengers and seven crew members and were killed.

In 1976, one passenger was killed when a 727 overran the runway after landing in Ketchikan.

The airline operates several flights from Puerto Vallarta, a resort on Mexico's Pacific coast, to San Jose, San Francisco and other California cities.