PORTO ALEGRE, Brazil – Flames raced through a crowded nightclub in southern Brazil early Sunday, killing more than 230 people as panicked partygoers gasped for breath in the smoke-filled air, stampeding toward a single exit partially blocked by those already dead. It appeared to be the world’s deadliest nightclub fire in more than a decade.

Witnesses said a flare or firework lit by band members started the blaze in Santa Maria, a university city of about 225,000 people, though officials said the cause was still under investigation.

Television images showed smoke pouring out of the Kiss nightclub as shirtless young men who had attended a university party joined firefighters using axes and sledgehammers to pound at windows and walls to free those trapped inside.