A teenager has been unconscious for six days after she inhaled toxic gas at a restroom in a fish market in Busan.

According to local police on Saturday, the 18-year-old was found unconscious around 3 a.m. Monday in the bathroom of the fish market near Gwangan Beach in Busan. 

She was discovered by her friend, who was waiting for her outside the restroom.

“She had not come out for 20 minutes,” the friend told police. “I also almost passed out twice and vomited a lot because of the smell of the noxious gas.”

The poisoned teenager was moved to the hospital but has not regained consciousness for six days.

Police detected an excessive amount of hydrogen sulfide in the air of the bathroom through initial investigations Friday.

The toxic gas is usually released from chemical reactions occurring in sewage, septic tanks and garbage dumps where wastewater deteriorates. Exposure to the gas could fatally affect the lungs.

Authorities assume the exhaust pipe in the building, believed to be more than 20 years old, was the source of the gas leakage.

Police are carrying out investigations with Korea Gas Safety Corp. and have requested the National Forensic Service to determine the exact amount of hydrogen sulfide at the scene.

Last December, three workers of a wastewater treatment plant died, and at least seven others fell unconscious from hydrogen sulfide exposure in Busan. The toxic gas was believed to have been produced when the workers poured alkaline wastewater into a well, the Busan Fire Department said.

By Choi Ji-won (jwc@heraldcorp.com)