Brazilian police say they are investigating whether Rio de Janeiro's state water utility may be committing environmental crimes by failing to treat sewage.

Officer Marcelo Prudente says police investigators visited at least six of Rio's main sewage treatment plants to take samples for testing.

The plants are located on lagoons in western Rio near the Olympic Park and on the sewage-polluted Guanabara Bay, where Olympic sailing events are to be held.

Prudente didn't elaborate on the technical aspect, but said the tests could lead to charges of environmental crime and larceny against the utility.

Thursday's police operation took place on the same day Rio Mayor Eduardo Paes inaugurated the revamped marina on the Guanabara Bay that is to be the starting point of the Olympic sailing competition.