Vice President Mike Pence, left, and US Ambassador to Ireland Edward Crawford speak to the media at the ambassador's residence in Phoenix park, Dublin, Ireland, Tuesday, Sept. 3, 2019.

House Democrats are investigating Vice President Mike Pence's stay at President Donald Trump's golf resort in Ireland, as well as Trump's recent promotion of another property he owns as a possible venue for the next G-7 summit.

In letters made public Friday, leaders of two Democrat-led House committees requested documents and other information from the White House, the Secret Service and the Trump Organization about the two matters. Both committees raised concerns about possible violations of the Constitution's so-called emoluments clauses, which bar federal officials from accepting payments from foreign governments or profiting beyond their salaries.

The new lines of inquiry are the latest in a growing list of investigations into the Trump administration, his current and former associates, his businesses, his 2016 presidential campaign and his inaugural committee that have been launched by state and federal prosecutors and Democrat-led House committees.

Pence opted to stay at the Trump International Golf Links and Hotel in Doonbeg, Ireland, during an official state visit this week. His meetings with Irish leaders, including Taoiseach Leo Varadkar, took place in Dublin – 180 miles from Trump's resort, noted House Oversight and Government Reform Committee Chairman Elijah Cummings, D-Md., in his letters.

The chairman asked for all documents related to the vice president's accommodations on that trip, including the total itemized costs that tallied up security, transportation, lodging and personnel expenses. He sent letters to Trump's acting chief of staff, Mick Mulvaney, Pence's chief of staff, Marc Short, Secret Service Director James Murray and the Trump Organization's chief financial officer, Allen Weisselberg.

"The Committee does not believe that U.S. taxpayer funds should be used to personally enrich President Trump, his family, and his companies," Cummings wrote.

He also asked for documents showing the cost of a prior visit to the Doonbeg resort in June by Trump himself. Cummings cited a Huffington Post analysis estimating that that trip cost taxpayers $3.6 million.

Spokespeople for Pence, the White House, the Trump Organization and the committees' Republican minorities did not immediately respond to CNBC's requests for comment.

Short had claimed Tuesday that Trump made a "suggestion" for Pence to stay at the club. The State Department "approved us staying there," Short said, calling it a "logical" choice. Trump later denied having any involvement in the decision.

In a statement following Trump's remarks, the vice president's office said, "At no time did the President direct our office to stay at his Doonbeg resort and any reporting to the contrary is false."