Police officers angered by the arrest of eight other officers caught on film while disposing of two bodies are suspected of killing 30 people in a shooting rampage in Brazil last week.
Police officers Fabiano Goncalves Lopes and Jose Augusto Moreira Felipe, who were arrested on Saturday, were seen near the drive-by shootings that left 30 people dead on the city outskirts, officials said.
Police had arrest warrants for two other suspects who were linked to the crime by witnesses who saw their composite sketches, Justice Minister Marcio Thomaz Bastos said in Brasilia, the nation's capital.
Mr Lopes and Mr Felipe were on medical leave from the police department at the time of the killings, said a spokeswoman for the Rio de Janeiro State Security Secretariat. Both had a history of disciplinary problems, she said.
Only two of the victims had criminal records and five were teenagers shot dead while playing video games at a local bar.
About 250 state police, aided by federal agents, continued to search for the other suspects across the Baixada Fluminense - a sprawl of poor suburbs on Rio's north side where the shootings took place.
Another 400 to 600 federal officers were expected to arrive in Rio this week to reinforce the investigation and to increase security in the region.
According to witnesses, the shooting started around 10pm on Thursday when four men got out of a silver Volkswagen and opened fire on the crowd at a street corner bar in Nova Iguacu. Fifteen people were found dead in and around the bar, and three more died in the hospital Friday.
The gunmen left the scene, firing randomly and killing two bicyclists along the road, then killed 10 people more in Queimados, a neighbouring town.