SYDNEY -- A plane heading to Shanghai returned safely to Sydney after an in-flight problem left a gaping hole in the engine casing.

China Eastern Airlines said the crew on Flight 736 noticed damage to the air inlet on the left engine after takeoff Sunday evening and the captain decided to return.

The airline said on its Sina Weibo microblog that the plane landed safety and the airline was taking care of passengers' needs. The A330 plane from Airbus has two engines.

Kathy Zhang, regional manager for China Eastern Airlines, told the Reuters news agency that the flight crew "observed the abnormal situation of the left engine and decided to return to Sydney airport immediately."

A China Eastern Airlines Airbus A330 aircraft sits on the tarmac at Sydney International Airport in Australia, June 12, 2017, after returning with a damaged left engine. REUTERS

Passengers told Australian media they heard a massive noise and smelled something burning.

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Passenger Ashley Beck told Australia's Channel Nine that after the passengers heard a loud noise, the crew started moving everyone from the left side of the plane.

Photos shared on social media showed a jagged, vertical hole in the side of the casing.

Jason Middleton, an aviation expert and professor at the University of New South Wales in Sydney, Australia, told the Australian Broadcasting Corp News that it appeared to him as though the engine casing had been torn off in front of the engine's main compressor blade.

In this image made from video, a hole is seen in the engine of China Eastern airlines Flight 736 after it landed in Sydney, Australia, June 12, 2017. AP

"When one of these things happens you often don't know how the damage began. It could have begun from loose screws," he said, according to the Reuters news agency.

"We went up in the air and all of a sudden we heard this noise ... it kind of smelt like burning. Oh, I was scared. Yeah, I was really scared. Our group was terrified," a passenger from the flight told Australia's Seven News network.

Another passenger told the Channel 9 network that the flight crew tried to calm down passengers and told them to put on their seatbelts after the loud noise.

"We were very panicked because we had no idea what was happening," she told Channel 9, according to Reuters.