BBC reports that a former governor of Rio de Janeiro says he helped pay a $2m (£1.6m) bribe to secure the Olympic Games for the Brazilian city in 2016.
Sérgio Cabral told a judge the payment was made to secure votes in the decision-making meeting in 2009.
He said that Carlos Nuzman, then the chairman of the Brazilian Olympic Committee, handled the negotiations.
In 2017, Mr Nuzman was arrested amid an investigation into the alleged vote-buying scheme. He denies wrongdoing.
Cabral is currently serving a 200-year sentence for several corruption cases.
On Thursday, he said the then-president of the International Association of Athletics Federations (IAAF), Senegal’s Lamine Diack, also served as intermediary in the alleged deal.
Mr Disco is to stand trial in France, having been arrested there in 2015. He has been accused of taking payments for deferring sanctions against Russian drugs cheats. He has previously denied wrongdoing, but has not yet responded to the latest allegations.
Both Mr Diack and Mr Nuzman were suspended from their roles, and later resigned.
Cabral also said Brazil’s then-president, Luiz Inácio Lula da Silva, had been informed after the money had allegedly changed hands.
Lula’s lawyers have said this is untrue. He has been jailed in a separate corruption case.
Ongoing criminal investigations into alleged bribery – led by prosecutors in Brazil and France – have already implicated Mr Nuzman, Mr Diack and his son, and then-IOC executive board member Frank Fredericks.
However, no leading officials have admitted involvement until now.
Cabral, who served two terms as Rio state governor from 2007 to 2014, spoke out during a hearing requested by his new defence team as he seeks a plea deal.
He hopes the information might reduce his lengthy sentences faced by him.
He was convicted of passive corruption, money laundering and embezzlement – linked t various cases from an exposé known as operation Carwash. His wife, Adriana Ancelmo, was also jailed after a period under house arrest.
Several high-powered Brazilian executives and politicians have recently reduced their sentences through plea bargains and giving evidence against others.
Cabral told investigators that his bribe had been aimed at winning the support of nine of the committee’s 95 members.
He implicated several top athletes who had voting rights. Olympic gold medallists Sergey Bubka and Alexander Popov have both since denied taking a bribe, and said they were considering suing for defamation.
Mr Bukba, a Ukrainian pole-vault champion, posted a series of tweets, in which he said he completely rejected “all the false claims made by the former Rio State governor”.
The ex-governor also said the money was provided by businessman Arthur Soares, one of his close friends, and transferred to Diack’s son, Papa Massata, who has previously denied wrongdoing.
Brazilian prosecutors charged Mr Soares – nicknamed King Arthur – for alleged involvement in bribery in 2017. He moved to the US during the investigations.