Three people were killed Monday in a gunbattle between drug gangs in a Rio slum that has been under police occupation for four months, Brazilian authorities said.

Police said none of their officers were involved in the pre-dawn violence in Rocinha, the city’s largest “favela.”

The sound of gunfire brought police to a home where they found three people dead and another wounded, as well as five handguns, three grenades, 1,500 small bags of cocaine, two-way radios and ledgers documenting drug sales.

The clash pitted subordinates of jailed Rocinha kingpin Antonio Francisco “Nem” Bonfim Lopes against members of a rival gang trying to take over drug corners in the favela, police said.

The shooting prompted police to beef up their already substantial presence in the hillside favela overlooking some of Rio de Janeiro’s most affluent neighborhoods.

Backed by 15 armored vehicles and seven helicopters, nearly 1,500 cops met no resistance when they occupied Rocinha last Nov. 13, but the community of roughly 72,000 people remains a hub of drug dealing.

The occupation is part of the Rio de Janeiro state government’s plan to pacify the city’s most violent favelas in preparation for hosting the 2016 Olympics.