PHOENIX  — No explosives were found on a Southwest Airlines plane that was diverted to Phoenix with 143 passengers on board, authorities said.

The FBI said Monday that an afternoon flight from Los Angeles to Austin, Texas, landed in Phoenix after someone called in a bomb threat.

Laura Eimiller of the FBI's Los Angeles field office said Flight 2675 left Los Angeles International Airport at 2:12 p.m. and was heading to Austin before the threat was received by telephone.

F-16s were scrambled out of Davis-Monthan Air Force Base in Tucson to monitor the flight as a precaution as it flew into Phoenix Sky Harbor International Airport, according to NORAD officials.

Flight 2675 landed safely at about 3 p.m., and authorities in Los Angeles asked Phoenix police to check out the possible threat.

The plane's crew and 143 passengers got off the plane and boarded several buses.

All passengers were interviewed by Monday evening, FBI special agent Manuel Johnson said in a statement. Investigators were making all efforts to identify the caller who made the bomb threat, he said.

The investigation continued Tuesday and no arrest has been made, Johnson said.

Sky Harbor spokeswoman Julie Rodriguez said the plane was isolated on the tarmac away from terminals.

Flights took off and landed only on the airport's two south runways Monday evening due to the investigation, and some arrivals were delayed, Rodriguez said.

The passengers from the diverted plane were flown to Austin on another flight, arriving early Tuesday morning, Southwest spokeswoman Katie MacDonald said.

The plane that was diverted was returned to service Tuesday, she said.