A federal police officer blocks the Rio-Niteroi Bridge, where armed police surrounded a hijacked passenger bus in Rio de Janeiro, Brazil August 20, 2019. (Photo: VCG)

RIO DE JANEIRO, Dec. 15 (Xinhua) -- Authorities found the bodies of seven men inside a vehicle in southern Rio de Janeiro state early Sunday, the Military Police said.

The victims were discovered in the town of Angra dos Reis, in a vehicle parked outside the local Fire Department.

Authorities suspect the crime is related to drug trafficking in the area.

Civilian police have opened an investigation into the case. Police said they don't yet know how the men were killed.

Bope, a special task force belonging to the Military Police, uncovered the bodies during an anti-narcotics operation in the area, which also led to the seizure of six firearms and two grenades.

The operation was carried out after rival criminal gangs clashed on Saturday, presumably over control of the local drug trade.

On Nov. 1, a different operation by the Military Police left eight people dead at a favela, or slum, in Angra dos Reis.