Police have arrested three people in connection with the nightclub fire that killed more than 230 people in southern Brazil, state media reported Monday.

They will be held for five days while authorities continue investigating Sunday’s deadly blaze, Marcos Viana, a police official, told state-run Agencia Brasil.

“We concluded that it was necessary to hold them prisoner temporarily, because we need their statements to help us clarify the incident,” Viana said, according to Agencia Brasil.

Police did not release the names of those arrested, Agencia Brasil said. They said their investigation into the fire at the Kiss nightclub in Santa Maria was continuing.

“We have much work ahead to clarify what happened and identify those responsible,” Viana said, according to the state-run agency.

At least 231 people died and hundreds more were injured in the fire, which authorities believe began about 2:30 a.m. Sunday when a band’s pyrotechnic show ignited insulation material.

Many apparently died from smoke inhalation. Others were trampled in the rush for the exits.

The owners of the nightclub have pledged to cooperate with the investigation into the fire, according to a statement released by the law firm of Kummel & Kummel.

“We are open to all authorities and inspections,” said the statement, obtained by Globo TV.

The club’s license had expired in August and had not been renewed, a local fire official told Globo TV.

The owners, however, said the nightclub was properly permitted and had been inspected by the fire marshal.

As investigators searched for the cause of the fire, coffins for the victims were lined up in a local gymnasium, which authorities have turned into a makeshift morgue.

On Monday, the first of Brazil’s three days of mourning, flowers were left outside the club in tribute to the victims, and a flag outside the country’s presidential palace flew at half-staff.

In Santa Maria, mourners lined up in a seemingly endless series of funeral processions.

By mid-day, the manager of the city’s municipal cemetery told CNN affiliate Band News that there had been 40 funerals there. By the end of the day, he said, there would be 70 more.

At one funeral, air force troops fired rifles in a tribute to a comrade who died not in battle, but in Sunday’s fire.

At another, two teenage brothers, the only children in one family, were buried side by side.

— CNN’s Shasta Darlington and Chelsea J. Carter contributed to this report.