The Rio 2016 cash-for-votes inquiry in Brazil has placed the International Olympic Committee under a fresh cloud of corruption less than a week before it is due to award the 2024 Games to Paris.

Almost two decades after its image took a battering with the Salt Lake City 2002 bribery affair the IOC finds itself at the centre of a new scandal.

It centres on Brazil's Olympics chief, Carlos Nuzman, who Brazilian officials on Tuesday accused of being the "lynchpin" in a plot to bribe the IOC into awarding Rio de Janeiro last year's Games.

Former IOC member Nuzman was taken in for questioning with his passport confiscated and his house searched.

Brazilian police say they are probing "an international corruption scheme" aimed at "the buying of votes for the election of (Rio) by the International Olympic Committee as the venue for the 2016 Olympics."

Rio won the right to hold South America's first Olympics, beating off competition from Madrid, Tokyo and Chicago at a 2009 IOC Congress in Copenhagen.

An arrest warrant was issued for Arthur Soares, a businessman who won lucrative pre-Olympics contracts from Rio's government.

One of his former associates was arrested in Rio and 11 properties were subjected to search and seizure raids. One of them was in Paris, French authorities said.

Prosecutor Fabiana Schneider told a press conference that Soares, known in Brazil as "King Arthur," allegedly bribed the son of disgraced Senegalese IOC member Lamine Diack before the 2009 vote in Denmark.

Diack, who was head of the International Association of Athletics Federations (IAAF) at the time, had considerable influence over African votes on the IOC.

Nuzman, Schneider said, had been the "lynchpin" between Soares and the son, Papa Massata Diack.

- Credibility at risk -

One seasoned Olympic observer told AFP on Wednesday the dramatic developments in Rio could prove a disaster for the IOC, depending on how the police inquiry evolved.

"The IOC can currently defend that it was the action of a rogue group masterminded by the Diack family," said Patrick Nally, the Briton who founded the IOC's 'TOP' sponsorship programme.

If however other IOC members are outed by having received similar payments from the Diack pot, and the claimed action regarding the Tokyo vote is evidenced, the IOC credibility will be in "tatters" as it will be going in the same direction as FIFA, with Salt Lake being seen as a mere "plaster over the cracks", he went on to warn.

"Taking Nuzmann down is one thing as it characterises that all the issues are Brazilian issues, naming more IOC members changes the matter significantly, but will the French with their Olympic trophy have the appetite to go further?"

The IOC appeared to be taken by surprise by news of the extensive Brazilian police operation on Tuesday.

"The IOC has learned about these circumstances from the media and is making every effort to get the full information," an IOC spokesman said at the organisation's headquarters in Lausanne.

"It is in the highest interests of the IOC to get clarification on this matter."

Brazilian investigators have worked closely with a similar French probe into the vote buying and French officials, including well-known anti-corruption judge Renaud Van Ruymbeke, attended the raid on Nuzman's home.

A lawyer for Nuzman, Sergio Mazzillo, said his client "says he did not act in an irregular way, that he did nothing wrong during the campaign."

The charges swirling around Rio's bid revive memories of the bribery scandal attached to the designation of Salt Lake City as the venue for the 2002 Winter Games.

That led to 20 IOC members being either kicked out of the Olympics' ruling body or pleading guilty to accepting bribes for votes.

That affair led to the IOC rewriting the rule book on how it went out about awarding future Games.

"Protecting the integrity of the candidacy process remains of the highest interest to the IOC as does identifying and punishing any infraction," the IOC recalled this week.

The IOC meets in Lima, Peru on September 13 to officially unveil Paris as the hosts of the 2024 Games with Los Angeles set to be attributed the 2028 Olympics.