RIO DE JANEIRO (AP) — Sailing's governing body may conduct independent water-quality tests in Rio de Janeiro's polluted Guanabara Bay, the sailing venue for the 2016 Olympics and the site of Rio's first test event in 2½ months.

Any hope Brazil would be able to clean up the sewage-filled bay soon was quashed in a document obtained by The Associated Press over the weekend.

In a May 7 letter to sports minister Aldo Rebelo, Rio's state environment secretary Carlos Francisco Portinho acknowledged in a best-case scenario that pollution flowing into the bay could be cut to "over 50 percent" — well below the promised reduction of 80 percent.

Alastair Fox, head of competitions for the international sailing federation, told the AP the body is likely to test on its own, hoping to allay athletes' health concerns.

The tests could also push Rio organizers to move more quickly on the problem.

Fox said he hoped the International Olympic Committee would do independent testing, although the IOC indicated to the AP it had no such plans.

"If the IOC are not conducting water-quality tests, then I think it is very likely the ISAF will," Fox said Monday in an email. "Certainly compared to most sailing venues, the water quality is very, very bad."

Danish Olympian Allan Norregaard, a bronze medalist at the 2012 Olympics, told the AP that Guanabara was "the most polluted place I've ever been." Other sailors interviewed by the AP called it an "open sewer."

The bay and similar concerns about Rio's iconic Copacabana and Ipanema beaches add to the disarray plaguing South America's first Olympics.

The IOC has sent a special troubleshooter to monitor progress, and last month IOC vice president John Coates said Rio's preparations were the "worst" in memory.

Spending on Rio has reached $17 billion and is expected to rise.

Nearly 70 percent of Rio's sewage goes untreated into its waters. Exposure to fecal matter can cause hepatitis A, dysentery, cholera and other diseases.

The visible problem involves old couches, tires and dead animals floating in the 148-square mile (383-square kilometer) bay. State officials are using garbage boats to collect floating debris, with the detritus weaving giant blankets of human and industrial waste along noxious shorelines.

"If someone picks up a bag, or hits a sofa or something like that, then clearly that is going to affect them in the race," Fox said.

"We've seen numbers from teams of the fecal content in the Guanabara Bay, which clearly are not safe," Fox added. "For us, that's a matter of concern. We've been assured again by the organizers that they are doing everything they can."

IOC spokesman Mark Adams said the Olympic body would not test.

"To confirm, we are not conducting any independent testing, as testing is already being done by Rio," Adams said in a brief email to the AP.

The IOC did not respond to repeated requests to interview IOC Medical Director Dr. Richard Budgett about potential health risks to athletes. In March, Nawal El Moutawakel, head of the IOC inspection team in charge of preparing Rio, said she had been assured the bay could be "clean from garbage."

"I don't think we will forgive ourselves if we let the athletes compete in an environment that is not safe and secure," she said.

Malcolm Page, a two-time Olympic gold medalist and chairman of the sailing federation's Athletes' Commission, said he trusted state tests, but welcomed independent testing.

"If the Brazilians are happy to receive any of that independent help, it only makes dealing with the problem easier and removes any sugar-coating," he said. "The sailors are certainly worried about it."

An analysis last year of a decade's worth of government data on Guanabara and other waterways showed that sewage pollution indicators consistently spiked far above acceptable limits, even under Brazilian laws that are far more lenient on pollution than those in the United States or Europe.

Fox said at least five courses — three inside the bay and two in the open Atlantic — would be used at the test event beginning Aug. 2. He said courses outside the bay had always been planned, not driven by the pollution problems.

Fox said plans call for the medal race — the final race where the gold, silver and bronze medals are decided — to be held in Guanabara near Flamengo Beach, a venue convenient for fans.

Signs around that beach warn against swimming.

Mario Moscatelli, a biologist and outspoken environmentalist, said retrieving the floating garbage in the bay was fine, but did not address the problem of untreated sewage.

In an open letter to Brazilian President Dilma Rousseff, he asked for the "release of the funds needed to recover the environmental assets, which are being used in Rio as garbage dumps and latrines."

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Associated Press writer Jenny Barchfield contributed to this report.

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Stephen Wade on Twitter: http://twitter.com/StephenWadeAP