An explosion Tuesday afternoon in a building in Sapporo’s Susukino entertainment district has left four people injured — with one man reportedly unconscious — according to media reports.

According to the reports quoting police and fire department sources, the incident occurred at around 3:20 p.m. in a girls’ bar on the second floor of a six-story building in a densely packed area of Susukino, lined with multitenant buildings.

An emergency call reported “an explosion and flames visible from a window,” NHK reported, citing the Sapporo Fire Department.

Seventeen fire trucks were dispatched to the scene. Footage from local broadcaster HBC showed white smoke billowing between buildings as firefighters sprayed water onto the flames. Approximately 70 square meters spanning the second and third floors were consumed by the fire.

The fire department confirmed that the injured include a man in his 40s who remains unconscious and three others, two men in their 30s and 50s and a woman in her 20s, who all sustained severe burns, NHK said.

Investigators are looking into reports that a gasoline-like liquid was found inside the premises. Police suspect arson may be the cause of the blaze and are questioning employees and patrons who were present at the time to determine the circumstances leading to the fire.