Brazilian prosecutors said there were "strong indications" football star Adriano transferred a large sum of money to a notorious drug lord held responsible for the downing of a police helicopter last year.
State prosecutors said in an e-mailed statement on Wednesday that after taking a deposition from Adriano, they would now request that a judge give them permission to examine data from the player's bank accounts and telephones.
Prosecutors said they were focusing on the alleged transfer last December of $ 33,000 from Adriano to a drug lord wanted by police.
"The Public Ministry considers extremely serious the facts that have made the player a suspect and there are strong indications that he has transferred money to the drug trafficker Fabiano Atanasio da Silva," the prosecutor's note read.
Officials are also looking into conspiracy to sell illegal drugs and the possession of unlawful weapons by organised crime groups as part of the investigation-though there was no indication Adriano was involved in those aspects of the case.
Adriano has denied any wrongdoing. He did not speak to the press after talking with prosecutors. After-hours calls to the office of the attorney who accompanied him to the prosecutor's office were not returned.
Adriano has not been charged with any crimes, and it was not clear what charges he could possibly face.
Late yesterday, a spokesman for Rio's civil police said they, too, were seeking a deposition from Adriano in connection to the same investigation.
Police say Silva - a leader of the Red Command drug gang - last October ordered his foot soldiers to overtake a rival gang's territory in a nearby slum. As the gangs fought a wild shootout, a police helicopter hovering nearby was shot down and crashed in flames, killing three officers.
That ignited a gang war and saw some 2,000 police invading more than a dozen slums, often triggering shootouts that left at least 40 people dead in less than a week. Bodies of rival drug gang members were strewn across streets of Rio, in shopping carts, trunks of cars or just dumped on the outskirts of slums.
That violence erupted two weeks after Rio won the right to host the Olympics and raised concerns about security for the Games.
The city, on October 2, was picked over Chicago, Madrid and Tokyo to host the games. Rio alone among the bid cities was highlighted for security concerns ahead of the International Olympic Committee vote.
Rio officials have defended their record in safely hosting major events - including the yearly Carnival and the 2007 Pan American Games. In addition, Rio police last year began an intense crackdown on the slums where drug gangs have ruled with impunity.
Police say Silva, who is not in custody, controls the Vila Cruzeiro slum where Adriano grew up and where he continues to spend time.
Last year, Adriano left Inter Milan, saying he was no longer happy playing football in Italy. He returned to Rio and signed with Flamengo, a team he led to Brazil's national championship last year.
Last week, Adriano announced that he was leaving Flamengo and returning to Italy, where he said he would sign with Roma.
It was not clear what impact the investigation would have on those plans.
The note from the prosecutor's office indicated that police had 60 more days to complete the investigation into Adriano's alleged involvement with the trafficker Silva.