SANTA MARIA, Brazil — A fast-moving fire roared through a crowded, windowless nightclub in southern Brazil early Sunday, filling the air in seconds with flames and a thick, toxic smoke that killed more than 230 panicked partygoers, many of whom were caught in a stampede to escape.

Inspectors believe the blaze began when a band's small pyrotechnics show ignited foam sound insulating material on the ceiling, releasing a putrid haze that caused scores of university students to choke to death. Most victims died from smoke inhalation rather than burns in what appeared to be the world's deadliest nightclub fire in more than a decade.

Survivors and the police inspector Marcelo Arigony said security guards briefly tried to block people from exiting the club. Brazilian bars routinely make patrons pay their entire tab at the end of the night before they are allowed to leave.

But Arigony said the guards didn't appear to block fleeing patrons for long. "It was chaotic and it doesn't seem to have been done in bad faith because several security guards also died," he told The Associated Press.

Later, firefighters responding to the blaze initially had trouble getting inside the Kiss nightclub because "there was a barrier of bodies blocking the entrance," Guido Pedroso Melo, commander of the city's fire department, told the O Globo newspaper.

Authorities said band members who were on the stage when the fire broke out later talked with police and confirmed they used pyrotechnics during their show.

Police inspector Sandro Meinerz, who coordinated the investigation at the nightclub, said one band member died after escaping because he returned inside the burning building to save his accordion. The other band members escaped alive because they were the first to notice the fire.

"It was terrible inside — it was like one of those films of the Holocaust, bodies piled atop one another," said Meinerz. "We had to use trucks to remove them. It took about six hours to take the bodies away."

Television images from Santa Maria, a university city of about 260,000 people, showed black smoke billowing out of the Kiss nightclub as shirtless young men who attended the university party joined firefighters using axes and sledgehammers to pound at the hot-pink exterior walls, trying to reach those trapped inside.

Bodies of the dead and injured were strewn in the street and panicked screams filled the air as medics tried to help. There was little to be done; officials said most of those who died were suffocated by smoke within minutes.

Within hours a community gym was a horror scene, with body after body lined up on the floor, partially covered with black plastic as family members identified kin.

Outside the gym police held up personal objects — a black purse, a blue high-heeled shoe — as people seeking information on loved ones crowded around, hoping not to recognize anything being shown them.

Teenagers sprinted from the scene after the fire began, desperately seeking help. Others carried injured and burned friends away in their arms. Many of the victims were under 20 years old, including some minors. About half of those killed were men, about half women.

The party was organized by students from several academic departments from the Federal University of Santa Maria. Such organized university parties are common throughout Brazil.

"There was so much smoke and fire, it was complete panic, and it took a long time for people to get out, there were so many dead," survivor Luana Santos Silva told the Globo TV network.

The fire spread so fast inside the packed club that firefighters and ambulances could do little to stop it, Silva said.

Another survivor, Michele Pereira, told the Folha de S. Paulo newspaper that she was near the stage when members of the band lit some sort of flare that started the conflagration.

"The band that was onstage began to use flares and, suddenly, they stopped the show and pointed them upward," she said. "At that point, the ceiling caught fire. It was really weak, but in a matter of seconds it spread."

Guitarist Rodrigo Martins told Radio Gaucha that the band, Gurizada Fandangueira, started playing at 2:15 a.m. "and we had played around five songs when I looked up and noticed the roof was burning."

"It might have happened because of the Sputnik, the machine we use to create a luminous effect with sparks. It's harmless, we never had any trouble with it," he said. "When the fire started, a guard passed us a fire extinguisher, the singer tried to use it but it wasn't working."

He confirmed that accordion player Danilo Jacques, 28, died, while the five other members made it out safely.

Police Maj. Cleberson Braida Bastianello said by telephone that the toll had risen to 233 with the death of a hospitalized victim. He said earlier that the death toll was likely made worse because the nightclub appeared to have just one exit through which patrons could exit.

Officials earlier counted 232 bodies that had been brought for identification to a gymnasium in Santa Maria, which is located at the southern tip of Brazil, near the borders with Argentina and Uruguay.

Federal Health Minister Alexandre Padhilha told a news conference that most of the 117 people treated in hospitals had been poisoned by gases they breathed during the fire. Only a few suffered serious burns, he said.

Brazil President Dilma Rousseff arrived to visit the injured after cutting short her trip to a Latin American-European summit in Chile.

"It is a tragedy for all of us," Rousseff said.

Most of the dead apparently were asphyxiated, according to Dr. Paulo Afonso Beltrame, a professor at the medical school of the Federal University of Santa Maria who went to the city's Caridade Hospital to help victims.

Beltrame said he was told the club had been filled far beyond its capacity.

Survivors, police and firefighters gave the same account of a band member setting the ceiling's soundproofing ablaze, he said.

"Large amounts of toxic smoke quickly filled the room, and I would say that at least 90 percent of the victims died of asphyxiation," Beltrame told the AP.

"The toxic smoke made people lose their sense of direction so they were unable to find their way to the exit. At least 50 bodies were found inside a bathroom. Apparently they confused the bathroom door with the exit door."

In the hospital, the doctor "saw desperate friends and relatives walking and running down the corridors looking for information," he said, calling it "one of the saddest scenes I have ever witnessed."

Rodrigo Moura, identified by the newspaper Diario de Santa Maria as a security guard at the club, said it was at its maximum capacity of between 1,000 and 2,000, and partygoers were pushing and shoving to escape.

Santa Maria Mayor Cezar Schirmer declared a 30-day mourning period, and Tarso Genro, the governor of the southern state of Rio Grande do Sul, said officials were investigating the cause of the disaster.

The blaze was the deadliest in Brazil since at least 1961, when a fire that swept through a circus killed 503 people in Niteroi, Rio de Janeiro.

Sunday's fire also appeared to be the worst at a nightclub since December 2000, when a welding accident reportedly set off a fire at a club in Luoyang, China, killing 309.

In 2004, at least 194 people died in a fire at an overcrowded nightclub in Buenos Aires, Argentina. Seven members of a band were sentenced to prison for starting the flames.

A blaze at the Lame Horse nightclub in Perm, Russia, killed 152 people in December 2009 after an indoor fireworks display ignited a plastic ceiling decorated with branches.

Similar circumstances led to a 2003 nightclub fire that killed 100 people in the United States. Pyrotechnics used as a stage prop by the 1980s rock band Great White set ablaze cheap soundproofing foam on the walls and ceiling of a Rhode Island music venue.

The band performing in Santa Maria, Gurizada Fandangueira, plays a driving mixture of local Brazilian country music styles. Guitarist Martin told Radio Gaucha the musicians are already seeing hostile messages.

"People on the social networks are saying we have to pay for what happened," he said. "I'm afraid there could be retaliation".