Brazilian police have arrested four people in connection with a fire at a nightclub that killed 231 people in the southern city of Santa Maria on Sunday.

A co-owner of the Kiss nightclub handed himself in to police on Monday afternoon for questioning.

Earlier, police held another owner of the club, a member of the band Gurizada Fandangueira, and its security chief.

More than 50 of the victims are being buried on Monday. Brazil has declared three days of national mourning.

The country’s deadliest fire in five decades reportedly started after a member of Gurizada Fandangueira, which was performing at the venue, lit a flare on stage.

Officials are also investigating claims that many of those who died were unable to escape as only one emergency exit was available.

The BBC’s Gary Duffy reports from Sao Paulo that the national sense of loss is profound. Most of the victims were students who died of smoke inhalation.

The government postponed a ceremony scheduled for Monday in the capital, Brasilia, to mark 500 days to the 2014 football World Cup. In Santa Maria, 30 days of mourning were declared.

President Dilma Rousseff, who cut short a visit to Chile, has been visiting survivors at the city’s Caridade hospital along with government ministers.

“It is a tragedy for all of us,” she said.

Authorities released the names of the victims, after revising down the death toll from 245.

More than 100 people were being treated in hospital, mostly for smoke inhalation.

‘Dark, heavy smoke’

The fire broke out as students from the Federal University of Santa Maria (UFSM) were holding a freshers’ ball, the Diario de Santa Maria, a local newspaper, reported.

A local journalist, Marcelo Gonzatto, told the BBC that the flare had “started a huge and fast fire that grew quickly and made a very dark and heavy smoke”.

“Lots of people couldn’t get out and died mainly because of the smoke not the fire,” he said.

Witnesses spoke of scenes of panic after the fire started, and a stampede as people tried to escape.

One, Mattheus Bortolotto, told local television: “It was sheer horror. The emergency exits did not work, and then I lost my friend in the confusion. Then a girl died in my arms. I felt her heart stop beating.”

A large number of victims were trapped in the club’s toilets, they said, possibly after mistaking them for an exit.

Survivors and police inspector Marcelo Arigony said security guards briefly tried to block people from leaving the club, the Associated Press reported. Bars in Brazil commonly make customers pay their whole tab at the end of an evening before they are allowed to leave.

One of the owners of the club is reported to have confirmed that they were in the process of renewing its licence to operate, and that its fire safety certificate had expired last year.

He is said to have received threats on the internet – as have surviving members of Gurizada Fandangueira.

Its guitarist, Rodrigo Martins, told local radio: “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. When the fire started, a guard passed us a fire extinguisher. The singer tried to use it but it wasn’t working.”

He said the band’s accordion player had died in the fire.

Brazilian broadcaster Globo said most of the victims were aged between 16 and 20.

A temporary mortuary was set up in a local gym as the city’s main mortuary was unable to cope.

Family members who came to identify the dead were led in one-by-one to see the bodies, Diario de Santa Maria reported.

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