Reuters reported the information, citing a source familiar with the document.
It noted that the notices were sent on Friday by the Office of Foreign Assets Control (OFAC) to shipowners in about 30 countries, which "represent the biggest step of its kind by the United States since Washington and its allies imposed a price cap aimed at restricting oil revenues to Moscow as punishment for its invasion of Ukraine."
At the same time, the Treasury Department would not comment on the investigation or enforcement actions, but pledged to "enforce the price cap and reduce Russia’s resources for its war against Ukraine.”
A source familiar with the reports said that some of the vessels under investigation were involved in unloading Russian oil from the Pacific port of Kozmino, while others were loading at the port of Primorsk in the Gulf of Finland.
One of the companies that received the request for information was reportedly Beks Shipping, based in Turkey. Reuters could not immediately reach Beks by phone for comment. The source did not name any other companies.
On October 12, the United States imposed sanctions on companies that tried to circumvent restrictions on the price of Russian oil.