A huge fire tore through the Rong Beer Na Ladprao music bar in northern Bangkok shortly before midnight on Sunday, killing at least 27 people and injuring 63 others, officials said. It is the Thai capital’s deadliest blaze in about 17 years.

Most of the dead were found trapped in windowless toilets near one of the rear exits, where they may have sheltered from the flames. Thai national police chief Kittharath Punpetch said the exit had not been used and people may have been obstructed by a table set up in the hall or by darkness.

Bangkok Governor Chadchart Sittipunt said the fire spread very rapidly and smoke was likely the main cause of death. Officials said there were signs that at least some exit doors might have been locked, and access to another exit near the kitchen may have been narrowed by shelving units.

Prime Minister Anutin Charnvirakul visited the site on Monday and said 27 bodies had been recovered. A musician told him he saw smoke coming from a circuit breaker near the stage before the power failed and an explosion was heard. Firefighters brought the blaze under control in about half an hour.