An Air China plane bound for New York was forced to return to Beijing on Wednesday after receiving a "threatening message" but nothing unusual was found, the airline and state media said.

Air China flight 981 returned to the Beijing Capital International Airport to "guarantee passenger safety", the airline said in a brief statement released through its official microblog after the flight landed.

An inspection of the plane turned up nothing abnormal and the flight was due to resume, the official Xinhua news agency said.

The flight originally took off at 1:00 pm (0500 GMT), Xinhua said, but did not say what time the plane turned back.

A microblog posting from an individual claiming to be a passenger said the plane was in the air for eight hours.

"After eight hours of flying, our flight just came back quietly to Beijing," said the posting under the name Natalie.

The airline's schedule shows flight CA981 bound for John F. Kennedy (JFK) International Airport was originally due to arrive in New York at 2:20 pm (1820 GMT) on Wednesday.

JFK's website said it had "no recent information" about the flight of the Boeing 747-400 aircraft.

Xinhua said police were investigating the incident and warned authorities would crack down on any illegal action.

In June, six members of China's Uighur minority tried to hijack a Chinese domestic flight departing from a restive city in the far-western Xinjiang region, but crew members and passengers thwarted them, authorities said.

The Tianjin Airlines plane, bound for the Xinjiang capital of Urumqi, returned safely to the airport in Hotan city after a struggle between the hijackers and the crew members and passengers.