Special counsel Robert Mueller subpoenaed President Donald Trump's businesses "in recent weeks" for documents, some of which relate to Russia, according to various reports.

The New York Times, citing two people briefed on the matter, first reported the subpoena.

The Times says it marks the first time Mueller, who is probing Russian involvement in the 2016 election, has asked for information directly related to the Trump Organization. The action comes as the former FBI director appears to be looking into the role foreign money could have played in the president's political activities, the newspaper reported.

It is unclear exactly what information Mueller requested. Trump and his lawyers have sought a swift end to the investigation, but the subpoena indicates it could continue for at least a few more months, the Times said.