Bomb-sniffing dogs later determined the item did not contain explosives, airport spokesman Harold Johnson said.
A Los Angeles Police Department bomb squad and the FBI still planned to search the plane, officials said.
Airport police received notification at 8:20 a.m. that there was a suspicious item on board the Los Angeles-bound plane which originated in Guadalajara, Mexico, said airport spokeswoman Nancy Castles. She said she did not know what the item was.
Johnson said the crew became alarmed when no one claimed the item.
"The flight attendant discovered an item and she said, 'Is this yours?' And all the passengers said, 'No," Johnson said.
The plane landed without incident just before 9 a.m., Castles said, and all 125 passengers and crew were transported to the terminal in buses after it taxied to a remote area of the airport.
"Passengers have been disembarked and carry-ons in the cabin will be screened by canines," said Transportation Security Administration spokesman Nico Melendez.