Australian media have reports that a passenger on board a plane from China to Australia discovered a note warning that a bomb would explode on the China Southern Airlines flight from Guangzhou to Sydney. The note was apparently found one hour into the journey, AAP reports.

The note forced the pilot to take emergency action and return to Guangzhou. Australian passenger Jason Harper said, "They dumped all the fuel. Then all the lights went out. But no-one knew what was happening. "Then we landed and there about 20 police cars and fire engines and stuff everywhere."

Authorities have confirmed Flight CZ325 from Guangzhou in China was turned around about an hour into the flight.

China Southern Airlines refused to release full details, but said a note was found, which "did reflect something of a dangerous item on board the plane… adequate to cause the tech crew to turn around and return to Guangzhou," reports The Sunday Times.

National Nine News said passengers were forced to leave the plane and were interviewed by authorities for two hours. They were later allowed back on board and resumed their journey.

Sydney Airport said the plane was now due to land at 3pm (Australian time) today. It was not known this morning how many people were on board the plane. A spokesperson for China Southern Airlines would only say it was “fairly full”.