A Brazilian nightclub was crammed with 1,000 people above its capacity before a fire tore through the building, killing at least 233, according to a report.

Fire official Guido Pedroso Melo told CNN the club likely had double its legal amount of patrons.

"When I arrived, we analyzed the preliminary scene and saw that there was a 1,000 maximum capacity but we understood there were about 2,000 there," he said.

Witnesses at the Kiss club, located in the southern city of Santa Maria, said that a flare or fireworks used by the band might have started the blaze.

Survivor Michele Pereira told the Folha de S. Paulo newspaper that she was close to the stage when the fire broke out.

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

Television images from the scene showed frantic rescuers pounding the club walls with sledgehammers in an attempt to reach those still inside, as black smoke filled the air.

De Melo told a local newspaper that firefighters had difficulty getting inside the club because “there was a barrier of bodies flocking the entrance.”

Police spokesperson Sandro Meinerz told media that the fire started Sunday morning. Along with the dead, at least 100 people were injured.

Earlier on Sunday, Maj. Cleberson Braida Bastianello said 245 people had died in the blaze. He later corrected the toll to 233, saying that the count was lowered after bodies were brought to a gymnasium for identification and the death of one victim who had been brought to hospital.

Rodrigo Martins, a guitarist with the band, said the fire broke out after they had played about five songs.

"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,” Martins told Radio Gaucha.

"When the fire started, a guard passed us a fire extinguisher, the singer tried to use it but it wasn't working.”

Martins confirmed that the band’s 28-year-old accordion player, Danilo Jacques, died in the fire, while the other five members survived.

Brazilian President Dilma Roussef left a summit of Latin American countries in Chile to fly to Santa Maria to visit victims.

“It’s a tragedy for all of us,” Roussef said.

The city’s mayor, Cezar Schirmer, has decreed a 30-day mourning period and governor Tarso Genro was scheduled to arrive in the city.

Officials are investigating the cause of the fire and are working to determine the total number of victims, police and regional government spokesman Marcelo Arigoni told Radio Gaucha.

Diario de Santa Maria – a local newspaper – said the fire broke out around 2 a.m. local time.

Club security guard Rodrigo Moura said the club was at full capacity with between 1,000 and 2,000 people inside at the time. He said the patrons were pushing and shoving to escape.

However, a local doctor who treated many of the survivors was told the club was filled far past its capacity. Survivors told Dr. Paulo Afonso Beltrame that the club was hosting a party for university students from the department of agronomy.

Beltrame said most of the dead suffocated.

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

"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."

Time correspondent Andrew Downie told CTV News Channel on Sunday that initially clubgoers were prevented from leaving by guards.

“In Brazil what normally happens is that when you’re in a club or a bar, you pay your bill at the end,” he said, adding that club security thought the patrons were trying to leave without paying.

“Once they learned it was a true fire, once they could see the smoke, they did open the doors. But it did seem to be a problem at the start.”

Downie also said local media reports indicated that the club’s fire certificate expired in August 2012.

“There are some irregularities at the club that need to be checked out in this case,” he said.

The fire occurred during one of the last summer weekends in Brazil, as students prepared to return to school, CNN’s Shasta Darlington told CTV News Channel.

“It’s just a shock. I mean nobody expected this. These are the summer months,” Darlington said.

Santa Maria is a major university city with a population of around 250,000.

The fire is one of the deadliest nightclub fires in more than a decade.

In 2000, a nightclub fire in Luoyang, China claimed the lives of 309 patrons. In 2004, at least 194 people died at an overcrowded nightclub in Buenos Aires, Argentina after a fire broke out.

With files from the Associated Press