The encounter is said to have occurred between the female and male youth teams of Esteghlal, a Tehran-based club with a mass following and under the overall authority of Iran's Islamic rulers.
The claims have embarrassed the management, which has denied any such match took place. Sensitivity has been heightened by Esteghlal's historic success and prestige - the club has twice won the Asian championship and was once closely linked to the monarchy under the shah, when it was known as Taj (crown). It was confiscated and renamed Esteghlal (independence) by the regime after the 1979 Islamic revolution.
The allegations prompted an internal inquiry. After a disciplinary hearing into the matter, the club announced that it had suspended and fined three officials, including the women's and youth team coaches. It also issued a public apology.
It is also being investigated by the state-run sports governing body that enforces separation of men and women in competitions and venues.
If proved, it could lead to the sacking of Mansourian, a former international who played for Iran in the 1998 World Cup finals in France. He is understood to be under pressure from the club's president, Amir Vaez Ashtiani, who has called for tough action against the possible culprits.
Iranian media reported the match finished with a score of 7-0 to the male team at Esteghlal's Marghoubkar stadium on Tuesday. Officials insist the two teams came into contact only briefly because their training sessions overlapped. Mansourian said the men's team wandered on to the playing field 10 minutes before the end of the women's session but were promptly ordered off by security staff.
"I was not present at the stadium but I heard that such an incident took place. However, on examination, I concluded that the incident did not happen in the way it is alleged," he said. "Esteghlal football club is committed to moral values and will take action against wrongdoers according to the law. Action will be quickly taken against those involved and the culprits will be legally punished."
Football is popular among Iranian women but religious regulations force female teams to play in closed spaces away from the gaze of male spectators. Women are also barred from attending men's football matches. A 2006 decision by Iran's president, Mahmoud Ahmadinejad, to allow women access was overturned after an outcry among conservative clerics, who claimed it contravened Islamic values of feminine modesty and chastity.