SANTA MARIA, Brazil -- There was no alarm, no working fire extinguisher, no sprinkler and almost no escape from the nightclub that became a death trap for more than 200 Brazilian college students.

As investigators began poking through the rubble and families mourned their dead, the university city in southern Brazil tried to understand how the Sunday morning blaze that killed 231 people could have been sparked in the first place, then rage rapidly out of control.

Why was there only one door available for exit and entry? What was the flammable material in the ceiling that allowed the conflagration to move so quickly? And, more pointedly, why was a band playing at the club allowed to use pyrotechnics inside the building?

Police were leaning toward the pyrotechnics as the cause of the blaze during a party at the Kiss nightclub organized by several academic departments at 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 with the pyrotechnics.

Firmino said the number and state of the exits is 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, also raises questions of whether Brazilian authorities are up to the task of ensuring safety in such venues as it prepares to host next year's World Cup and the 2016 Olympics.

Some critics have said conditions in many Brazilian bars and clubs are ripe for another deadly blaze. They say that in addition to modernizing sometimes outdated safety codes and ensuring sufficient inspectors, people must change their way of thinking and respect safety regulations.

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 the newspaper O Globo said on its website that a fourth person had surrendered to police. 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.

Vieira declined to identify those detained, but local media has identified them as two co-owners of the club and two members of the band that was using a spark machine inside the building when the fire erupted.

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.

"A problem in Brazil is that there is no control of how many people are admitted in a building," said Joao Daniel Nunes, a civil engineer in nearby Porto Alegre. "They never are clearly stated, and nobody controls how many people enter these night clubs."

Rodrigo Martins, a guitarist for the group Gurizada Fandangueira, 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.

"I felt that something was falling from the roof and I looked up and I saw the fire was spreading, and I shouted 'Look, it's catching on fire, man, it's catching fire,'" Martins said. "Then the drummer tried to throw water on it, and it looked like the fire spread more then. Then the security guards came with an extinguisher, tried to use it, but it didn't work."

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

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

Standing next to 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. Martins said he thought Jacques made it out of the building and later returned to save his accordion.

The first funeral services were held Monday for the victims, including brothers Pedro and Mercello Salle. 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 and could die.

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.