The Airbus A321-200 plane landed safely at around 12:40 p.m. (0340 GMT). It had set off from the holiday island of Jeju an hour earlier, the airport’s flight schedule showed.

No one was hurt in the incident but nine people, all teenagers, were sent to hospital after suffering breathing issues, a Daegu fire department official said.

“I thought the plane was going to explode … It looked like passengers next to the open door were fainting,” an unidentified 44-year-old passenger told the Yonhap News Agency.

The passenger said the cabin crew had made an in-flight announcement asking if there were any doctors on board.

A video aired on television, reported to have been shot by a passenger, showed the moments before the landing, with a door open and wind rushing in as passengers sat nearby.

The transport ministry said in a statement police had taken into custody the man who had opened the door and authorities were investigating violations of aviation safety laws.

The ministry did not say why he had opened the door.

A transport ministry official told Reuters authorities were looking into whether Asiana Airlines had followed protocols to manage emergency exits.

The official said it was possible an emergency exit could be disarmed near the ground when the pressure inside and outside the cabin were similar.

The plane was two or three minutes away from landing when the male passenger sitting next to an emergency exit opened a cover and pulled a lever so the door opened about 200 metres (656 ft) above the ground, an Asiana spokesperson said.

All onboard were seated with seat belts fastened because the plane was about to land, the spokesperson said.