The plane, a single-engine Cessna 172 , went off the radar at McCarran International Airport about 7:15 p.m., said Ian Gregor, spokesman for the Federal Aviation Administration.

It was the second small plane that disappeared from local radar Thursday night. The same thing had happened with a single-engine Beechcraft Bonanza at 6:37 p.m. Authorities later learned that plane had made a successful emergency landing several miles southeast of Jean, and its two occupants, who were headed to Phoenix from Las Vegas, were unhurt, Gregor said.

A Las Vegas police air unit was searching the area around Mount Potosi when the crew heard an explosion and saw a plane burning on the mountain, Lt. Steve Herpolsheimer said.

The crash was estimated to be about 2,000 feet from the top of the 8,514-foot tall mountain, Herpolsheimer said.

Search and rescue crews tried to get to the crash site using four-wheel-drive vehicles, he said. Rescue air units were also sent out to the site, said Las Vegas police spokesman Bill Cassell.

Late Thursday, police were considering pulling back and waiting until daylight to try to reach the crash site.

Cassell said he had no idea why the Civil Air Patrol plane was flying Thursday night. The most common mission for the Civil Air Patrol is search and rescue.

The crew of this plane was not believed to have been searching for the missing Beechcraft, so perhaps they were involved in a training flight, Cassell said.

Civil Air Patrol representatives could not be reached for comment late Thursday.

Mount Potosi is known as the site of a 1942 plane crash in which actress Carole Lombard and 21 other people died.

Lombard, the wife of actor Clark Gable, had been returning to California after taking part in a national war bond campaign for World War II when the plane she was in, a twin-engine DC-3, slammed into a cliff near the top of the mountain.

Review-Journal staff writer Henry Brean contributed to this report. Contact reporter Beth Walton at bwalton@reviewjournal.com or (702) 383-0279.