Four people have been arrested in connection with a Brazilian nightclub fire that killed 231 people over the weekend.

At a news conference Monday, police Insp. Ranolfo Vieira Jr. said the arrests are for investigative purposes and come with a five-day limit.

The club’s owner and two band members who were performing at the club are among the detained.

The blaze, which engulfed the crowded Kiss nightclub in Santa Maria early Saturday morning, may have been caused by a pyrotechnics display igniting exposed overhead sound insulation.

The club violated many state safety codes: fire extinguishers were not placed at every 1,500 square feet throughout the club and there was only one exit. Also, there was no fire alarm, no sprinklers and no fire escapes.

Also on Monday, a military brigade official said the death toll from the blaze now stands at 231, many of them younger than 20 years of age including several minors. Police Maj. Cleberson Braida Bastianello subsequently told The Associated Press by telephone that the toll had risen to 233.

Brazilian President Dilma Roussef has declared a three-day national period of mourning for the victims, while Santa Maria Mayor Cezar Schirmer has declared a month-long period of mourning in the southern Brazilian city.

Accounts of the fire paint a picture of panic and confusion, as a fire extinguisher failed to work, and smoke prevented those attempting to flee from finding the club's single working exit.

Many of the dead were found trapped in the venue's two bathrooms, where it is believed the victims -- most of whom died from smoke inhalation rather than burns -- wound up in a mistaken hunt for a way out.

Further compounding the tragedy, there are reports that security guards were at first unaware of the fire and focused on preventing patrons from leaving without paying their bills.

"It was chaotic and it doesn't seem to have been done in bad faith because several security guards also died," police inspector Marcelo Arigony told The Associated Press.

Rodrigo Martins, a guitarist with the band playing onstage when the blaze erupted, told Radio Gaucha that their set began at approximately 2:15 a.m. local time Saturday.

They had played about five songs, he said, when he noticed the ceiling in flames.

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

Other members of the band escaped except for 28-year-old accordion player Danilo Jacques, who investigators say had initially left the club. Jacques died after returning inside to retrieve his accordion.

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

Time magazine correspondent Andrew Downie told CTV's Canada AM that when emergency responders arrived they found bodies piled up inside the exits, some apparently trampled in the rush to flee the building.

Questions are emerging, Downie said, about whether the club had sufficient emergency exits, whether they were properly illuminated and if security guards were trained to help people exit in the event of an emergency.

Fire official Guido Pedroso de Melo told a local newspaper that firefighters had difficulty getting inside the club because "there was a barrier of bodies blocking the entrance."

After leaving a summit of Latin American countries in Chile to fly to Santa Maria on Sunday, President Roussef said, "It’s a tragedy for all of us."

Santa Maria is a major university town with a population of approximately 260,000.

The fire is the deadliest in Brazil since a 1961, when 501 people after flames swept through a circus in Niteroi, Rio de Janeiro. It’s also one of the deadliest nightclub fires anywhere in the world, in more than a decade.

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

In alarmingly similar circumstances, tragedy also struck at a Perm, Russia nightclub in 2009, when an indoor fireworks display ignited a plastic ceiling decorated with branches. And 100 people died at a Rhode Island nightclub in 2003, after pyrotechnics set the walls and ceiling covered in soundproofing foam alight.

With files from The Associated Press