A Pacific Southwest Airlines commuter jet crashed yesterday in the coastal mountains 175 miles northwest of Los Angeles, shortly after the crew radioed that they heard gunshots. All 44 people on board were killed.

"Just west of Paso Robles, the crew reported gunshots in the back of the plane," Drucella Anderson, a spokeswoman for the National Transportation Safety Board, said. Authorities said that an engine breakup on the same type of commuter aircraft last year sounded like gunfire. In that incident, also involving PSA, no one was injured.

The pilots of Flight 1771, making a commuter run from Los Angeles to San Francisco, apparently reported to controllers "we've got a problem" and mentioned gunshots, a source close to the investigation said.

Eight seconds later, according to the source, controllers asked the pilots to clarify what they had said. The pilots repeated that they heard gunfire on the plane. They also reported smoke in the cabin.

Immediately afterward, about 4:15 p.m. local time, controllers lost radio and radar contact with the plane. The plane was being directed by controllers from the Oakland Air Route Traffic Center.

The plane was flying at 22,000 feet at the time, said Fred Farrar, a Federal Aviation Administration spokesman.

The NTSB dispatched a "go team" to the scene, about 15 miles west of Templeton, Calif., to investigate the cause of the crash. Board member Patricia Goldman will accompany the team. Investigators from the Federal Bureau of Investigation also were sent to the scene, said Sue Schnitzer, an FBI spokeswoman at the agency's headquarters here.

The plane, a four-engine British Airways Corp. 146, was sighted with flames coming out of its side over Templeton, shortly after radio contact was lost, Washington Post staff writer Jay Mathews reported from Los Angeles.

The BAC-146 is a high-wing turboprop, used mainly for short-haul travel.

Bill Hartzell, a cattle rancher in Santa Rita, said his daughter watched the burning wreckage come down on his ranch, the Associated Press reported. She notified the authorities, who sealed off the area.

A spokesman for the San Luis Obispo County Fire Department said plane parts, luggage and victims were spread out over 10 acres.

Bill Vargas, who was driving by at the time of the crash, told the AP, "I saw a streak drop out of the sky about 3,000 feet. It appeared to be a large flame heading straight down to the ground at a very high rate of speed."

He said the plane disappeared behind a hill.

Rescue workers combed the wreckage site in the Santa Lucia mountains, which run parallel to the Pacific coastline, until well after nightfall in a vain search for survivors. The rescue attempt was hampered by rugged terrain and darkness, officials said.

A PSA spokesman said the plane was carrying 39 passengers and five crew members. The plane seats 83.

Bill Hastings, a spokesman for PSA, said two of the crew members were pilots and the other three were flight attendants.

The AP reported that PSA said it called 25 employes into its headquarters last night to notify relatives of the victims.

The plane left Los Angeles International Airport at 3:36 p.m. local time and was scheduled to arrive at San Francisco International Airport at 4:43 p.m., Hastings said.

About a year ago, the NTSB investigated an incident involving the same model aircraft, operated by PSA. The plane experienced an uncontained engine failure -- in which the engine lost a blade, and pieces of it were embedded in the plane's fuselage. When the blade pieces hit the side of the plane, the noise was similar to gunshots, the source said.

No one was injured in last year's incident, but the plane's fuselage was damaged.

That incident occurred during a flight between Los Angeles and Reno, Nev., Hastings said. The flight was diverted to Fresno, where it landed without incident, he said.

He said the airline has 24 of the BAC-146 models in its fleet and has been operating them since 1984.

The crash is the second in the airline's 39-year history. The first crash occurred in 1978 over San Diego, when a PSA Boeing 727 and a small, private plane collided, killing 144.

PSA merged at the end of May with USAir, but the two airlines are still operating as separate companies, Hastings said.

Yesterday's crash was the third major U.S. aircraft disaster this year. On Nov. 15 a Continental Airlines DC9 crashed on takeoff from Denver's Stapleton International Airport, killing 28 persons. On Aug. 16, 156 people were killed when a Northwest Airlines MD80 crashed on takeoff from Detroit Metropolitan Airport.