Ground transportation during last week's visit to Ireland by US Vice President Mike Pence cost US taxpayers almost $600,000 (€545,000).
The figures are contained in State Department receipts released by the US government.
The decision by Mr Pence to stay at the Trump International Golf Links and Hotel in Doonbeg, Co Clare has been criticised by Democrats who accused him of funnelling US taxpayers' money into a Trump business.
The US House Oversight Committee has launched an investigation into the matter and has highlighted the fact that the Trump hotel in Doonbeg is located 290km from Dublin, where Mr Pence's official meetings were taking place.
Last week, Mike Pence's Chief of Staff Marc Short said that Donald Trump had suggested staying at the hotel but Mr Trump denied this was the case.
The US House Oversight Committee has requested documents and information from the White House, the office of the Vice President, the Secret Service and the Trump organisation in a bid to establish how the decision was made and how much the stay at Trump Doonbeg cost.
The committee is also investigating if the hotel stay was a violation of the US constitution's emoluments clauses, which prohibit US presidents from receiving additional income on top of their salaries.