Heavy pollution lies along the edge of Guanabara Bay, the venue for the Olympic sailing.

Police have recovered a human leg from the Rio waters close to the Olympics sailing course.

The discovery comes soon after New Zealanders were racing in the area.

The Daily Mail reported that residents of Ilha do Governador called police after they saw the leg bobbing in waters near the coastline.

It was reportedly a male leg, which had been chopped off at the hip.

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Police said it had the name "Kauan" tattooed on the calf.

A member city's homicide police department told the Daily Mail: "'The leg was taken away to be examined. Samples will be taken in case anyone comes forward to report anyone missing.

"But they will not be compared with lists of people already reported as missing. It is very common to find body parts in the Guanabara Bay.

"It was probably someone murdered by the drugs gangs who was dumped in one of the rivers that flow into the bay."

The Olympic sailing waters drew heavy criticism ahead of the Games because of pollution problems.

There was a report of an arm floating in the sailing venue waters in late February.

Late last week Belgian sailor Evi Van Acker, who won a bronze medal in the Laser Radial class at the 2012 Olympics, became the first sailor to fall ill, allegedly because of the poor water quality in Rio.

Her coach believes Van Acker's latest problems stem from earlier problems when she contracted a severe intestinal infection while training in Rio in July.

"Evi caught a bacteria in early July that causes dysentery," coach Wil Van Bladel told Britain's Telegraph newspaper.

"Doctors say this can seriously disrupt energy levels for three months. It became clear that she lacked energy during tough conditions. She could not use full force for a top condition ... the likelihood that she caught it here during contact with the water is very big."