The government of the country's biggest city, Sao Paulo, promised tougher security regulations for nightclubs and other places where many people gather. President Dilma Rousseff promised Monday that "we have the responsibility to make sure this never is repeated."

Mayors in other cities promised to follow suit, especially with the upcoming start of Carnival, which floods nightclubs with celebratory crowds.

Meanwhile, G1, Globo television network's internet portal, said police searched two other Santa Maria nightspots owned by Mauro Hoffmann, one of the co-owners of the Kiss nightclub, for evidence that could help shed light on the investigation.

Monday night's searches yielded no evidence and the site reported that computers that stored images recorded by Kiss club's security cameras were not found in the rubble.

A judge has frozen the assets of both of the club's owners, pending the investigation.

The actions added to a national sense that the early Sunday nightclub fire marked a possible turning point for a country that's long turned a blind eye to safety and infrastructure concerns. One of Brazil's biggest newspapers, O Globo, published an editorial Tuesday saying it was time for action.

"The tragedy in Santa Maria forces us to seriously reflect over our national culture of leniency, contempt and corruption," it said. "We must start from the principle that the mea culpa belongs to us all: public servants, owners of establishments that disregard safety regulations, and regular citizens who flaunt them."

Preliminary investigations into the tragedy have revealed that there was no alarm, working fire extinguisher or sprinkler and only one working exit in the Kiss nightclub, turning it into a death trap.

Police were leaning toward the idea that pyrotechnics set off by a band playing at the time was the cause of the blaze, which killed dozens of students from the Federal University of Santa Maria. Inspector Antonio Firmino, part of the team investigating the fire, said it appeared the club's ceiling was covered with an insulating foam made from a combustible material that ignited.

Firmino said the number and state of the exits are under investigation but that it appeared that a second door was "inadequate," as it was small and protected by bars that wouldn't open.

The disaster, the worst fire of its kind in more than a decade, raises questions of whether Brazilian authorities are up to the task of ensuring safety in such venues as the country prepares to host next year's World Cup and the 2016 Olympics.

Hundreds of people marched peacefully outside the nightclub Monday night to remember the victims, and demand justice. Some carried signs with slogans such as, "May God's justice be carried out."

"We hope that the justice system, through its competent mechanisms, succeeds in clarifying to the public what happened, and gives the people an explanation," said marcher Eglon Do Canto.

Brazilian police said they detained three people Monday in connection with the blaze, while Brazilian media indicated two members of the band Gurizada Fandangueira and the club's two co-owners had been detained. Police Inspector Ranolfo Vieira Junior said the detentions were part of the ongoing police probe and those detained can be held for up to five days.

According to state safety codes here, clubs should have one fire extinguisher every 1,500 square feet as well as multiple emergency exits. Limits on the number of people admitted are to be strictly respected. None of that appears to have happened at the Santa Maria nightclub.

Rodrigo Martins, a guitarist for the group Gurizada Fandangueira, which was playing that night, told Globo TV network in an interview Monday that the flames broke out minutes after the employment of a pyrotechnic machine that fans out colored sparks, at around 2:30 a.m. local time.

He added that the club was packed with an estimated 1,200 to 1,300 people.

"I thought I was going to die there," Martins said. "There was nothing I could do, with the fire spreading and people screaming in front."

Standing near the stage when the fire broke out, Rodrigo Rizzi, a first-year nursing student, watched the tragedy unfold.

"I was right there, so even though I was far from the door, at least I realized something was wrong," he said. "Others, who couldn't see the stage, never had a chance. They never saw it coming."

As he headed toward the door, the air turned dense and dark with smoke; there was no light, nothing pointing to the single exit. Rizzi found himself clawing through a panicked crowd that surged blindly toward the door.

"I was halfway across the floor, I could see the door, but the air turned black with this thick smoke," he said. "I couldn't breathe. People started to panic and run toward the door. They were falling, screaming, pulling at each other."

Witnesses said security guards who didn't know about the blaze initially blocked people from leaving without paying their bills. Brazilian bars routinely make patrons pay their entire tab at the end of the night before they're allowed to leave.

Inside the club, metal barriers meant to organize the lines of people entering and leaving became traps, corralling desperate patrons within yards of the exit. Bodies piled up against the grates, smothered and broken by the crushing mob.

About 50 of the victims were found in the club's two bathrooms, where the blinding smoke caused them to believe the doors were exits.

Martins confirmed that the group's accordion player Danilo Jacques, 28, died, while the five other band members made it out safely.

Most of the dead were college students 18 to 21 years old, but they also included some minors. Almost all died from smoke inhalation rather than burns.

National Health Minister Alexandre Padilha cautioned that the death toll could worsen dramatically, telling news media in Santa Maria on Monday that 75 of those injured were in critical condition.

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 anywhere in the world since December 2000, when a welding accident reportedly set off a fire at a club in Luoyang, China, killing 309 people.