The U.S. has asked at least one shipping insurer for information on 14 companies it suspects may have violated sanctions on Russian oil, a sign Western governments are still trying to limit the ways Moscow exports its fuels.

The American Club — one of a dozen main firms insuring ships against risks such as oil spills and the only to be based in the U.S. — confirmed it received a request for information from the Treasury Department’s Office of Foreign Assets Control and passed that onto its members.

Under a policy imposed by the Group of Seven nations and its allies, traders can buy Russian oil as long as it’s below $60 a barrel. If crude exceeds that price cap, then Western companies are prohibited from providing services such as insurance and shipping, which has seen many traditional providers step away. 

The notice said that OFAC had reason to believe some of the 14 companies may have violated the price cap. Some of those entities are already on OFAC’s sanctions list.

It’s not the first time the U.S. has reached out to shipping-services providers about the price cap. Late last year, the Treasury sent letters to oil-tanker companies it suspected may have violated the cap, threatening “criminal fines, imprisonment or both.”

The Treasury didn’t immediately respond to a request for comment.