A total of 54 people were hospitalized when carbon dioxide released from fire extinguishers engulfed a courthouse in the western city of Balıkesir Monday.

The cause of the leak is being investigated while four among those affected by the gas remain in critical condition, authorities announced.

Balıkesir Governor Ersin Yazıcı told reporters that large-sized extinguishers in the basement floor of the courthouse were "activated" though there was no fire in the building.