SEOUL: South Korean police have launched an investigation after Asiana Airlines said a passenger opened a door on a flight shortly before the aircraft landed safely in the city of Daegu on Friday.

The Airbus A321 plane landed at Daegu airport at around 12:40 p.m. (0340 GMT) after departing from the island of Jeju an hour earlier, the airport's flight schedule showed.

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

Eight of those taken to hospital were schoolchildren from Jeju, according to Jeju's education office.

Authorities were questioning a passenger near an emergency exit row, Asiana officials said.

"Police are investigating the incident after a passenger who was sitting near the emergency exit said he touched its lever," one of the officials said.

The plane was two or three minutes from landing when a male passenger sitting next to an emergency door 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 added.