(CNN) The House Oversight Committee has been investigating for several months whether increased military expenditures benefiting the Trump Turnberry golf course and resort in Scotland represent a conflict of interest for the President, according to committee documents.
But the Defense Department has refused to comply with investigators' requests to date, a senior Democratic committee aide told CNN on Friday.
The newly revealed investigation, which was first reported on Friday by Politico, represents yet another front at which House Democrats are probing President Donald Trump's finances and businesses, with various Democrat-led panels pushing new or existing probes going into the 2020 election season.
In a June letter to then-acting Defense Secretary Patrick Shanahan, Oversight Committee Chairman Elijah Cummings and fellow Democratic Rep. Jamie Raskin detailed their investigation into the golf course and nearby Glasgow Prestwick Airport.
They allege that the airport, a key location as the closest airport to Turnberry, has seen an uptick in military spending since Trump won the presidency. Both Turnberry and the airport have operated at significant losses over the past few years.
"Despite Prestwick Airport's struggling operations, US military expenditures at the airport appear to have increased substantially since the election," the lawmakers wrote.
They cite records of the Defense Logistics Agency showing 629 fuel purchase orders adding up to $11 million since October 2017, as well as reports of the Prestwick airport providing discounted rooms to some crews and free rounds of golf at Turnberry for American — specifically military — crews.
"Given the President's continued financial stake in his Scotland golf courses, these reports raise questions about the President's potential receipt of US or foreign government emoluments in violation of the US Constitution and raise other serious conflict of interest concerns," Cummings and Raskin wrote. "In order to fulfill its responsibilities under the Constitution, the Committee is seeking information related to expenditures at both Prestwick Airport and the President's nearby Scotland golf resorts."
CNN has reached out to the Pentagon and Air Force for comment.
The committee requested all documents related to military expenditures at both Turnberry and Prestwick, as well as all communications between Defense Department employees and Turnberry representatives.
A senior Democratic committee aide told CNN that the Defense Department has not cooperated with the investigation.
"The Defense Department has not produced a single document in this investigation," the aide told CNN on Friday. "The Committee will be forced to consider alternative steps if the Pentagon does not begin complying voluntarily in the coming days."