An ambulance airplane crashed in a remote, mountainous area near the Mexican (searchborder early Sunday, shortly after taking off from a small San Diego air field, killing all five people on board, authorities said.

The Learjet carried two pilots, two paramedics and a nurse on a flight bound for Albuquerque, N.M., said Larry Levy, CEO and medical director of Albuquerque-based Med Flight Air Ambulance, which owned the aircraft.

The plane went down around 12:30 a.m., about two miles east of Brown Field. It was the company's first crash since starting operations in 1979, he said.

Emergency personnel had to hike to the largely inaccessible crash site, said Larri Frelow, an operations manager for the Federal Aviation Administration.

The cause of the crash had not been determined. The FAA (searchand National Transportation Safety Board were investigating, Levy said.

The crew was returning to Albuquerque after carrying a patient from Mexico to San Diego, Levy said. The airstrip just north of the border is used as a port of entry for private aircraft arriving in California from Mexico and by military and law enforcement aircraft.

Radio contact was lost just one minute after takeoff, Levy said.

Med Flight Air Ambulance suspended operations "to give the crews time to debrief and cope with the circumstances," Levy said. The company has about 100 employees at bases in Albuquerque; El Paso, Texas, and Las Vegas, Nev.

The company withheld the names of the victims, but Levy said four were based at Albuquerque and the fifth worked out of El Paso.