An explosion that occurred while fire was being extinguished at a bathhouse in Busan has left some 20 people injured, including two firefighters.

The fire in the bathhouse, located in Busan’s Dong District, was reported at around 1:40 p.m. Friday, with the main blazes appearing to be suppressed after 20 minutes.

A sudden explosion inflicted harm on 21 people who were nearby the bathhouse, with two firefighters reportedly suffering serious injuries, including burns to their faces, while Dong District chief Kim Jin-hong was also hurt during an inspection of the site and is being treated at the hospital.

Fire authorities have issued a Level One response and mobilized some 100 personnel to put out the fire while restricting access to the area over concerns of further blasts.

Police and fire authorities believe the explosion occurred in the basement of the building that contains the bathhouse on its fourth floor. They plan to determine what caused the fire after blazes are fully extinguished.