Three factory workers were killed and another hospitalized after a gas leak in a factory in northern Türkiye late Sunday.

A worker was checking a filtration valve in a gelatin factory in Bolu province’s Gerede district when he was exposed to poisonous gas. Three workers went to the valve room to check on their co-worker. When one of them emerged from the room semi-conscious, other workers in the factory alerted emergency services. Firefighters donning masks managed to bring three workers out of the room but all died at the scene while E.K., the worker who managed to barely escape the room was taken to the hospital. Three firefighters exposed to the gas while evacuating the workers were also hospitalized.

Disaster and Emergency Management Authority (AFAD) crews detected a high concentration of hydrogen sulfide, ammonium and carbon monoxide at the scene.

Speaking to reporters after visiting the factory, Gerede Mayor Mustafa Allar said the room the workers walked in had a small, shallow pool and the victims were found there. He said that the surviving victim was still in a critical condition.