(CNN) A passenger plane carrying 163 people was forced to turn back 40 minutes into the flight after it was discovered one of the plane's doors was not completely shut.

The flight, operated by low-cost Korean Air subsidiary Jin Air, left Cebu in the Philippines on Sunday, bound for Busan in South Korea.

A public relations officer with Jin Air confirmed the incident to CNN, saying a noise alerted staff to a gap in the door, prompting the pilot to return to Cebu.

At the time of the incident the Boeing 737-800 was at an altitude of 10,000 feet.

According to the Jin Air officer, an inflight announcement was made to inform those on board the flight.

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