Referee Ibrahim Chaibou of Niger is free to officiate matches while FIFA investigates his handling of an international exhibition between Nigeria and Argentina that is suspected of being manipulated.

World soccer's governing body said Wednesday that it is too early in its probe to suspend Chaibou from duty.

''FIFA has not opened a formal disciplinary proceeding into this matter, but is at the stage of 'pre-investigation.' Therefore, no provisional suspension can be pronounced,'' the governing body said in a statement.

Chaibou awarded Argentina a penalty for handball in the eighth minute of injury time in the team's 4-1 loss in Nigeria last Wednesday.

FIFA said it was studying betting patterns during the match as ''part of a wider ongoing FIFA investigation.''

In May 2010, Chaibou gave three penalties for handballs in South Africa's 5-0 win over Guatemala in Polokwane that was the World Cup host's final warmup match.

Chaibou was the referee when Bahrain beat a fake Togo team 3-0 last September. That match appeared to confirm growing fears that international matches were being targeted for fixing by organized crime gangs.

The Niger referee joined FIFA's approved list of international officials in 1996 and must stand down this year after reaching the mandatory retirement age of 45.

Responding to the spread of match-fixing, FIFA and its six confederations now have power to veto unsuitable referee appointments, and require organizers of international fixtures to provide details of match officials two months before kick off.