A mysterious American plane seen at an airport in Iran may have violated U.S. law by landing in Tehran, which the Treasury Department will investigate.

U.S. law "would generally prohibit U.S. registered aircraft from flying to Iran," State Department spokeswoman Jen Psaki told reporters Friday. "The Department of Treasury will look at this and see if there is a concern here."

The plane is owned by the Bank of Utah, but that hardly clears things up. “We have no idea why that plane was at that airport,” bank executive Brett King told the New York Times.

"Even some former federal officials, who spoke on the condition of anonymity, said the very presence of an American-flagged aircraft parked in broad daylight suggested its flight had been approved as part of a legitimate business trip. What is more, they said, the easily identifiable plane was not likely to be part of a covert diplomatic mission," the Times added.

Psaki emphasized that Treasury would determine "if there was any violation of sanctions here — I'm not predicting there was," she told reporters.