The initial report by the Iranian news agency Fars said a Falcon jet entered Iranian airspace from Turkey "despite repeated warnings" from Iran. The Fars report said the passengers and crew were released after questioning revealed they unintentionally strayed into Iran's airspace while flying to Afghanistan.

The U.S. Air Force said the initial Iranian claim seemed erroneous and no U.S aircraft were reported missing, The New York Times reported. The Air Force said it was investigating the reports to make sure that no U.S. warplanes had landed in Iran.

Shortly after the Fars report, the Iranian state-run television channel, al-Alam, said on its Web site the plane "was not a military plane and did not belong to the United States" and that a plane was forced down on Sunday and allowed to fly to Afghanistan Monday, the Times said.

A subsequent al-Alam report quoted an unidentified Iranian military source as saying the plane was Hungarian and carried no United States military personnel, the Times said. Hungary has a small military presence in Afghanistan, where U.S. and NATO forces are fighting Taliban militants.