An Air Canada flight has been forced to return to Sydney airport, although an airport official could not confirm reports of a fire on board the plane.

Sydney airport spokesman Michael Samaras said Flight AC34 bound for Vancouver and Toronto landed safely at Sydney airport early in the afternoon.

Sydney's Daily Telegraph reported that a fire broke out in the plane's galley and could not be contained.

The newspaper reported the plane dumped fuel before landing.

Mr Samaras said he did not know why the plane turned back. He said he had not received any reports of a fire on board.

No one on Flight AC34 was injured in the incident, said Jeannie Foster, Air Canada's general manager for Australia and New Zealand.

"There was smoke seen by a crew member in an oven so the captain made the right decision and decided to come back to Sydney to check it out as a safety precaution," Ms Foster said.

"They had to dump fuel because it's a very heavy airplane with 15 hours worth of fuel to get to Canada."

Ms Foster denied earlier reports of a fire breaking out on board.

"There was no fire at all," she said.

The flight was carrying 264 passengers.