Investigators with special counsel Robert Mueller have asked the White House for documents related to former national security adviser Michael Flynn, according to a report Friday.
The Times reported that prosecutors have been investigating Flynn's business dealings with a Turkish-American businessman who worked with Flynn past year, and are trying to determine if the Turkish government was behind payments to Flynn.
Mr Flynn, a former lieutenant general in the United States army, failed to register as a foreign agent when Flynn Intel Group signed a $600,000 contract with Mr Alptekin's Dutch company Inovo BV in August 2016.
Reportedly, Mueller and his team are now investigating not only whether Flynn failed to report his links to a foreign government as required by law or if he had illicit ties with Russian elements, but all of Flynn's business connections throughout the campaign.
Flynn resigned after less than one month in office for failing to fully disclose the details of his December communications with the Russian ambassador in Washington to White House officials.
A transcript of intercepted calls between Mr Flynn and Mr Kislyak revealed they had discussed USA sanctions imposed when former President Barack Obama concluded that Moscow had interfered in the U.S. election campaign.
Prosecutors have also asked during interviews about Flynn's speaking engagements for Russian companies, for which he was paid more than $65,000 in 2015, and about his company's clients - including work it may have done with the Japanese government. The document request is the first known instance of the special counsel asking the White House to hand over records. Trump has publicly stated in the past that he believes Mueller should restrict his investigation on Russia's involvement in the election and not expand into his or his associates' finances.
While Mr Mueller steps up his investigation, Donald Trump has again angrily denied that his campaign team colluded with the Kremlin.