The probe follows revelations that US military funds were spent in the president’s Turnberry golf course.
The House Oversight and Government Reform Committee is probing financial transactions at the property and nearby Glasgow Prestwick Airport.
Elijah Cummings, chair of the committee, has raised ”serious conflict of interest concerns” over the spending.
The Democratic congressman wrote to Patrick Shanahan, then-acting Secretary of State for Defence, in June, over the allegations.
“Two years before the 2016 election, President Trump spent hundreds of millions of dollars to purchase and renovate theTurnberrygolf course in Scotland,” Mr Cummings wrote.
“To date, the property has continued to suffer financial losses and has not turned a profit for the president of his companies.
“The airport closest to the TrumpTurnberrygolf course – Glasgow Prestwick Airport – has been viewed as integral to the golf course’s financial success, yet it too has lost millions of dollars every year since its purchase by the Scottish Government in 2013.”
Mr Cummings said he was concerned over military spending at the golf course, which appeared to have ”increased substantially since the election”.
In the document Mr Cummings cited news reports, which alleged the airport had offered “cut-price rooms for select passengers and crew” and free rounds of golf at Turnberry.
His committee is demanding to see all financial documents held by the department of defence in relation to the property.
The panel has been investigating the matter since April, according toPolitico.
“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,” Mr Cummings said.
“In order to fulfil 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.”
The department of defence has not co-operated with the committee’s request, according toCNN.
But records from the Defence Logistics Agency reveal that the military spent $11m (£8.9m) on fuel at Prestwick Airport, despite it being cheaper for the planes to refuel at US military bases.
“Glasgow Prestwick Airport is operated on a commercial basis and at arm’s length from the Scottish Government, in compliance with European Union state aid rules,” a Scottish Government spokesperson said.
“Ministers do not intervene in the commercial discussions at the airport.
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“The senior management team at the airport has been tasked with all aspects of taking the airport forward, including building on existing revenue streams.
“Glasgow Prestwick Airport has handled military and private flights since the 1930s and it remains an important part of the airport’s business”.
News of the investigation emerged a day after Democrats requested documents about Mike Pence’s stay at one of the president’s properties in Ireland.
The vice president stayed at Mr Trump’s Doonbeg resort during a recent trip to Ireland.
The property was located 181 miles from meetings he was scheduled to attend in Dublin with Irish officials.
A series of letters the House Oversight Committee sent to the White House, the Trump Organisation, the vice president’s office and the US secret service following the trip said the committee “does not believe that US taxpayer funds should be used to personally enrich President Trump, his family, and his companies”.
Additional reporting by agencies