SYDNEY, Australia (AP) _ A United Airlines flight from Australia to Los Angeles was forced to return to Sydney International Airport late Tuesday afternoon after a threat, media reported, citing federal police.

The flight, which took off about 1 a.m. EDT was 90 minutes into the flight when the pilot made the decision to return to Sydney, an airline spokesman told Australian Associated Press.

He would not detail the nature of any problems.

The flight landed safely in Sydney at about 3:45 a.m. EDT and Australian Broadcasting Corp. radio reported passengers were being bussed off the aircraft at an isolated part of the airport.

Federal police told Seven News that the plane had received an unspecified threat.

The Boeing 747 was reportedly carrying about 200 passengers.

Roads leading to the airport also reportedly were closed off.

No further details were immediately available.