WASHINGTON (Reuters) – The U.S. Treasury Department has sent notices to 30 shipping carriers requesting information on ships suspected of carrying Russian crude oil sold for more than the cap imposed under sanctions over the Ukraine war, according to a source who viewed the documents.

The Office of Foreign Assets Control has sent notices to management companies in about 30 countries requesting information on more than 100 vessels, the source said.

It is the largest such measure taken by the United States since Washington and its allies imposed a cap on Russian oil at $60 a barrel last year, she added.

Requests for information are a routine step in sanctions investigations.

The Treasury Department did not immediately respond to a request for comment.

The G7, the European Union and Australia imposed a cap on maritime exports of Russian crude last December in order to punish Moscow for its war against Ukraine. It prohibits Western companies from providing services such as transportation, insurance and financing for oil sold above the cap.

The price cap has led to a shift in global markets, with China and India now buying Russian oil, much of which had traditionally been destined for Europe and other markets. This year, much of Russian oil has traded above the ceiling as global oil prices have risen.

U.S. officials said the cap imposed additional costs on Russia due to a “shadow fleet” of aging tankers, longer voyages and a reliance on non-Western maritime services, which reduces the income it can devote to war.

(Reporting Timothy Gardner; Gaëlle Sheehan, editing by Kate Entringer)

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