LOS ANGELES — The pilot of a small plane told air traffic controllers he had lost an engine before the aircraft crashed on a busy freeway near a Southern California airport and exploded into flames, injuring the pilot and his fiancé.

“Mayday, mayday!” the pilot shouted to air traffic controllers before the Cessna 310 aircraft crashed Friday morning on Interstate 405, just short of a runway at John Wayne Airport in Costa Mesa. “I lost my right engine.”

The dramatic exchange was captured on a recording of air traffic controller communications, posted on the website LiveATC.net.

The Federal Aviation Administration said the pilot had declared an emergency shortly after taking off from the airport and was trying to return when the plane crashed on the freeway. The official cause of the crash is still under investigation, FAA spokesman Ian Gregor said.

The male pilot and his fiancé — who are in their 50s and 60s — were alive when an off-duty firefighter pulled them from the fiery wreckage, Orange County Fire Capt. Larry Kurtz said.