MANILA, JUNE 26 -- A Philippine Airlines passenger plane crashed into a fog-shrouded mountain and burst into flames today about nine miles from its destination in northern Luzon, killing all 50 people aboard.

U.S. Embassy spokeswoman Mary Carlin said at least one American and possibly as many as 10 were among the 46 passengers on the twin-engine HS748 turboprop. Airline officials said most of the others were Filipinos.

Government television said nine passengers were Americans of Filipino descent. {The airline said five of the victims were members of a Filipino-American family returning home for a visit, Reuter reported.}

The embassy withheld names of known or suspected American victims until their citizenship was verified and their families notified. But Texas Instruments said John B. Neill, 47, president and director of the Dallas-based company's Philippines operations, was killed in the crash. A company spokesman in Dallas said Neill had worked for the company for 25 years.

Airline Vice President Ricardo Paloma called it the second worst commercial aviation accident in the Philippines. Another PAL HS748 crashed in northern Luzon in 1967, killing 56 people.

Leslie Espino, senior vice president of the airline, said the flight from Manila was approaching the mountain resort of Baguio City, 130 miles north of the capital, when pilot Rosauro Bustamante radioed that visibility was poor.

The plane disappeared from radar screens 10 minutes before it was scheduled to land. Search planes located the wreckage five hours later, 200 yards below the summit of a 7,000-foot peak, about nine miles south of the airport.

Antonio Babijes, director of the Rescue Coordination Center, said two U.S. Air Force helicopters reached the site early in the evening and found no survivors. Three helicopters were sent from the U.S.-operated Clark Air Base, 50 miles north of Manila, to assist in rescue operations.

Richard Aspillaga of Benguet Management Corp. said by telephone from Baguio City that lumberjacks from his company were first on the scene and pulled a survivor from the wreckage, but he died soon afterward. Aspillaga said the fuselage was intact and the flames apparently trapped victims inside.

Espino, the airline official, said the cause of the crash had not been determined but "one could not rule out weather as a contributory cause." He said recovery of bodies was suspended because of darkness and bad weather and would resume Saturday.

It was the first crash of a scheduled commercial airliner in the Philippines since 1975, when 33 people died in a PAL crash at Las Pinas, southeast of Manila. A U.S. Air Force C135 crashed in 1964, after takeoff from Clark, killing 75.