An American bank purchased a Boeing aircraft last month from an Iraqi company with ties to Iran, aviation records show. The Bank of Utah bought the 737 from Iraq's Al Naser Airlines, which has sold aircraft to Mahan Air -- a company that reportedly transports weapons and soldiers from the Islamic Revolutionary Guard Corps to Syria. The purchase took place Oct. 20, but records do not indicate where the plane is currently located.

Al-Naser Airlines was blacklisted by the U.S. in May when it sold aircraft to Mahan Air, which has provided financial, material and technological support to the forces supporting Syrian President Bashar Assad. The recent transaction appears to violate U.S. sanctions. The Bank of Utah is a community bank with 13 branches throughout the state. Officials at the bank did not reply to an International Business Times request for comment.

The reason for the purchase remains unclear. This is not the first time the Bank of Utah has purchased aircraft with ties to Iran. In 2014 an aircraft purchased by the bank showed up at Mehrabad Airport in Tehran. At the time, Bank of Utah executive Brett King said: "We have no idea why that plane was at that airport."

Since January 2014, the Bank of Utah has been listed as the purchaser of 10 aircraft: four of them from Boeing, aviation records show, the rest from McDonnell Douglas, an American aerospace manufacturing corporation and defense contractor. 

Now, the bank appears to have made a purchase from one of the only airlines in the world still selling to Iran.

In October 2011, the Treasury Department announced that Mahan Air would be sanctioned for its support of the Quds Force, which backs Assad. The airline was also accused of flying Quds Force members linked to a plot to kill Saudi Arabia’s former ambassador to the U.S., Adel al-Jubeir. 

Then, six months ago, the Treasury Department took punitive action against Al-Naser Airlines for selling Boeing aircraft to Mahan. The department froze American-held assets of Al-Naser.

The U.S. Office of Foreign Asset Control, a group in the Department of Treasury, has listed both Al-Naser Airlines and Mahan Air on its Specially Designated Nationals List of people, organizations and vessels with whom U.S. citizens and permanent residents are prohibited from doing business. 

Despite its presence on the SDN List, Mahan Air and Al-Naser Airlines have been able to continue selling both American manufactured aircraft or aircrafts with American parts. 

One of Iran’s commercial airlines last month bought a jet that was manufactured in the U.K. with a Honeywell engine, IBT learned. The latest deal marked the second time in five months that the Iranian airline purchased aircraft to expand its fleet based in Tehran, Iran, despite being blacklisted by the U.S. since 2008. The transaction underscored the airline’s intention to expand the company through new subsidiaries. But as the airline expands, the U.S. is struggling to keep up.

Over the years, the Commerce Department has intercepted several third parties attempting to sell to Mahan Air. Still, the department is unable to stop every transaction. Senior U.S. officials told IBT recently that they are investigating the purchase of a U.K.-manufactured aircraft by one of Iran’s airlines. Because the jet has an American-made engine, it is subject to U.S. export laws.