Prosecutors in Brazil say they have identified four police officers who allegedly tortured a bricklayer in a Rio de Janeiro favela.
Amarildo de Souza has not been seen since 14 July, when he was questioned by officers investigating drug-related activities in the Rocinha shanty town.
Witness accounts and a recording of a phone call have helped identify the four main suspects.
The case shocked the country and led to protests against police brutality.
Another 15 members of the same squad, known as a "pacifying unit", were charged on Tuesday.
A total of 25 officers, including three women, have been charged in connection with the disappearance of Amarildo de Souza.
Investigators say witnesses placed the four accused policemen inside the container in which Mr Souza was taken for questioning.
Prosecutors allege that Mr Souza was allegedly subjected to electric shocks and drowned in a bucket inside the container.
He disappeared after the questioning.
Voice analysis of a recorded telephone call placed days later concluded that another officer tried to pass himself off as a drug-trafficker supposedly admitting to the killing of Mr Souza.
The case has drawn attention to allegations of police violence in the "pacification" of Rio's favelas.
Critics say there are a large number of disappearances in Rio which are not adequately investigated.
The officers say they released Mr Souza and that they had nothing to do with his subsequent disappearance.
But the prosecution argues they hid the body and cleaned up the evidence of torture in the container.
The 'pacification units' were created to regain state control of favelas run by drug lords ahead of the 2014 World Cup and the 2016 Olympic Games.
Their alleged involvement in Mr Souza's disappearance has led to protests in Rio and other cities, both in Brazil and abroad.