WASHINGTON — Republican lawmakers on the House committee investigating the fatal Benghazi attacks in 2012 are traveling to Europe as part of their inquiry.

The committee declined to release details about the trip for security reasons, but Democrats say Republicans are embarking on “a lavish and expensive new congressional delegation to Italy and other European destinations.”

The Republican-led House Select Committee on Benghazi, which heard testimony from former Secretary of State Hillary Clinton last month, is already facing criticism for costing taxpayers millions.

It has proven more costly than permanent panels on intelligence, veterans affairs, ethics and small business, according to the Committee on House Administration, which collects monthly expenditure reports from each committee. Democrats have a website constantly calculating the cost of the committee: $5 million so far.

“In the 11-hour marathon hearing with Secretary Clinton, Republicans showed the world that the Benghazi Select Committee is a taxpayer-funded fishing expedition to derail Secretary Clinton’s presidential campaign – and that their net came up empty,” said Rep. Elijah Cummings of Maryland, the top Democrat on the committee.

Republicans say the committee’s expenses includes Democrats’ spending even though they have not tried to help further the investigation or access documents the Obama administration has not provided.

Democrats say the House committee already has access to information about Department of Defense actions in Libya through testimony and hearings conducted by the House Armed Services Committee.