U.S. federal authorities are investigating investment advisory firm Concord Management, which oversaw hedge fund investments worth billions of dollars for Russian billionaire Roman Abramovich, the New York Times reported Tuesday.

The investigation, being conducted by the Securities and Exchange Commission (SEC) and the Federal Bureau of Investigation (FBI), is partly focused on how Abramovich's associates used several offshore shell companies to invest $8 billion in hedge funds and private equity firms, the report added, citing people close to the firm. https://nyti.ms/3p3x646

The authorities are seeking information about the flow of money to and from more than a dozen shell companies based in havens like the British Virgin Islands and the Isle of Jersey, the NYT report said.

Earlier in June, a U.S. court issued warrants for the seizure of two luxury planes owned by Abramovich.

The U.S. Department of Justice is also seeking broader authority from Congress to seize Russian oligarchs' assets as a means to pressure Moscow over its invasion of Ukraine, a prosecutor said in July.

In March, a KleptoCapture task force was launched to enhance the United States' ability to punish wealthy Russians whom Washington accuses of enabling Russian President Vladimir Putin to invade Ukraine.

The SEC, the FBI, and Concord Management did not immediately respond to Reuters' requests for comment.