Newt Gingrich’s campaign has reimbursed the former House speaker for more than $300,000 in travel expenses.

The payments have caught the attention of the Federal Election Commission, which reviews campaign reports for compliance with the law. The commission sent Gingrich’s campaign two letters asking for more detail on where the money was actually spent.

The letters state that payments like those to Gingrich should also list the ultimate recipient of the funds, the business where the expense was incurred. Staff of the campaign were similarly reimbursed for hundreds of thousands of dollars worth of travel expenses, bringing the total amount in question to over $600,000.

A campaign spokesman did not return a request for more information on the payments, but Lisa Lisker, Gingrich’s campaign treasurer, wrote in a response to the FEC that the law does not require more detail on the payments.

“The Committee has reviewed all reimbursements to individuals for travel and subsistence,” Lisker wrote, “and confirms that no further itemization is required under any Commission regulations for these expenditures.”

Jason Torchinsky, a former counsel to President George W. Bush’s reelection campaign who is representing a super PAC backing Rick Santorum this year, agreed that the Gingrich campaign is not required to list more detail on the payments. The letters from the FEC over the issue are commonplace, he said, and typically ignored by campaigns because regulations do not actually require the additional detail.

The letters from the FEC were first reported by the Washington Times.