Authorities investigating Bangkok’s deadliest nightclub fire in nearly two decades say most of the victims were found trapped inside windowless bathrooms, where they are believed to have sought refuge from thick smoke and rapidly spreading flames.

The fire tore through the Rong Beer Na Ladprao late Sunday, killing at least 27 people and leaving dozens more injured.

Firefighters took approximately 30 minutes to bring the blaze under control after it erupted at the popular music venue in northern Bangkok.

City officials said at least 25 people remain hospitalized in critical condition.

Bangkok Governor Chadchart Sittipunt said preliminary findings indicate that most victims died from smoke inhalation.

By Monday morning, authorities had sealed off the site as forensic investigators combed through the wreckage in search of evidence to determine the cause of the fire.

The building’s front-facing windows had been blown out by the intense heat, while the surrounding sidewalk was strewn with debris, including burned televisions, loudspeakers and a charred electric guitar.

Inside the venue, shattered windows revealed burned tables still lined with empty beer bottles, underscoring how quickly the fire engulfed the establishment.

The venue, which describes itself as a brewery and beer hall, is capable of accommodating up to 600 patrons, although officials have not confirmed how many people were inside when the fire broke out.

According to Bangkok’s Erawan Emergency Medical Center, 73 people were injured in the incident.

While emergency services initially reported 27 fatalities, Bangkok city authorities later placed the death toll at 28.

National Police Chief Kittharath Punpetch said investigators found most of the victims inside windowless bathrooms located near one of the venue’s rear exits.

Authorities believe many fled there in an attempt to escape the flames but became trapped by smoke.

Kittharath said the nearby emergency exit appeared to have gone unused. Investigators are examining whether a table positioned in a hallway to sell candy obstructed access or whether the heavy smoke and darkness prevented patrons from locating the exit.

Officials have launched a full investigation to determine the cause of the blaze and whether safety violations contributed to the high death toll.