Officials said the arrests are for investigative purposes. They did not release the names of the people in custody.
According to Zero Hora newspaper, a lawyer says his client Elissandro Spohr, a co-owner of the club, was arrested. The paper also says two band members were arrested.
The death toll from Sunday's fire at Kiss nightclub in Santa Maria is at least 231. Many of the victims were under 20 years old, including some minors. The first funerals of victims were planned for Monday.
Survivors told investigators the security guards briefly tried to block patrons from leaving the club through the only exit because they wanted everyone to pay their bills.
The bodies of the victims also slowed firefighters trying to get inside.
The fire was reportedly set off by band members sending pyrotechnics into foam sound insulation material. If true, the band could face manslaughter charges.
The fire broke out sometime before 3 a.m. Sunday and the fast-moving blaze and toxic smoke engulfed the club within seconds.
The Associated Press contributed to this report.