A judge in Argentina has started legal proceedings against the owner of the disco where nearly 200 people died in a fire last month.
Relatives blame poor safety standards
Omar Chaban, who owns Cromagnon in the Argentine capital, Buenos Aires, is accused of manslaughter and faces up to 25 years in prison.
The judge also froze $20m worth of Mr Chabran's assets.
Thousands of Argentines took part in a protest on Monday in Buenos Aires, to mark a month since the fire happened.
Some called for the mayor, Anibal Ibarra, to resign.
Thousands had previously marched to protest against the city government in Buenos Aires, which they blame for poor safety standards.
The fire at Cromagnon Nightclub was one of the worst disasters in Argentine history. About 700 people were injured.
It started when someone at the nightclub launched a flare during a concert, but the disaster was compounded by the conditions inside.
The club was reported to have been filled beyond its capacity and some of its emergency exits were said to have been locked.
Two officials have already stepped down after accepting responsibility for inadequate safety measures.
But Mr Ibarra refuses to resign, saying the fire brigade is responsible for building safety in Buenos Aires, and it approved the nightclub in June.
He has also blamed the club owner.