Fifa says it is investigating unusual betting patterns relating to Nigeria's 4-1 win over Argentina in Abuja on Wednesday.
When the score was 4-0 in the friendly game, a large number of bets were placed on there being a fifth goal.
Only five minutes of injury time were shown, but eight had elapsed when Mauro Boselli scored a contentious penalty given against Joseph Yobo for handball.
Fifa said in a statement: "This match was one we had an active interest in."
And the Nigerian Football Federation, which organised the match, said it would help Fifa's investigation and also set up its own inquiry.
"We will put all these measures [the inquiry] in place in the spirit of fair play and transparency," NFF General Secretary Musa Amadu said in a statement. "But we would still insist that, until it is proven beyond doubt, we believe that we won this match fair and square.
"There remains, to the best of our knowledge, no untoward motives to this game than to play it fairly and win it fairly."
Argentina's involvement in the Copa America tournament meant they sent a largely sub-strength side, captained by Manchester City defender Pablo Zabaleta.
Ike Uche opened the scoring after 10 minutes, with Victor Obinna adding a second from the penalty spot before Uche headed a third before half-time.
Eight minutes after the restart Emmanuel Emenike lobbed a fourth goal, and the fifth goal of the match, refereed by Ibrahim Chaibou of Niger, came with the final kick of the game.
The match took place the same day Fifa president Sepp Blatter was re-elected for a fourth term in office, pledging to improve the image of the game around the world.