A small private plane carrying a load of marijuana strayed into President Obama's no-fly zone over Los Angeles on Thursday and was forced to land at Long Beach Airport after being intercepted by U.S. Air Force jet fighters, authorities said.

The four-seat Cessna entered the restricted airspace about 11 a.m. as the president was flying from Orange County to Los Angeles aboard Marine One, a military helicopter provided for his use. Federal officials said the aircraft was never close enough to endanger Obama.

Air traffic controllers tried repeatedly to contact the single-engine Cessna, authorities said, but the pilot did not respond. The plane was quickly intercepted by two F-16 fighters from March Air Reserve Base in Riverside County, they said.

After the Cessna touched down, federal agents and Long Beach police detained the pilot for questioning and found what law enforcement officials described as a large amount of marijuana on board the aircraft.

The pilot was taken into custody by Long Beach police, but his identity and other details were not released because of the continuing drug investigation.

Aircraft are typically prohibited from flying within 10 miles of any plane or helicopter carrying the president.

Brian Leary, a spokesman for the United States Secret Service, which provides protection for the president, said the plane violated temporary restrictions that had been imposed by the Federal Aviation Administration for Obama's visit.

Pilots who violate airspace restricted for security reasons can face revocation of their flying certificates, FAA officials said. If illegal drugs are found onboard, the aircraft can be confiscated by law enforcement agencies.

After his morning fundraisers, Obama departed from Los Angeles International Airport about 2:45 p.m. and flew to San Francisco, White House officials said. They declined to comment on the airspace violation.

It was not clear who was piloting the Cessna, which according to federal records was manufactured in 1961. The plane's FAA registration lists the owner as David W. Major, 52, of Grover Beach, a town south of Pismo Beach in San Luis Obispo County.

Major holds a student pilot certificate issued in 2008, according to the FAA. He could not be reached for comment Thursday.