Reps. James Clyburn (D-S.C.), Maxine Waters (D-Calif.), Carolyn Maloney (D-N.Y.) and Stephen Lynch (D-Mass.) wrote to Secretary of Defense Mark Esper on Friday and said they were investigating whether his agency “inappropriately used hundreds of millions of taxpayer dollars appropriated by Congress.” The investigation will be carried out by the House Oversight and Reform Committee, the Select Committee on the Coronavirus Crisis, and the Financial Services Committee.

“As Congress considers additional coronavirus relief legislation, Americans deserve to know that the Trump Administration is following the law and using relief funds for their intended purpose—to aid the nationwide pandemic response,” the lawmakers wrote.

Congress provided the Pentagon with $1 billion in March to “prevent, prepare for, and respond to coronavirus” under the Defense Production Act, which allows the government to compel U.S. companies to manufacture products in the nation’s interest. Although the Pentagon did spend some of the money on masks and swabs, $688 million was ultimately allocated towards the defense industrial base, mostly for projects that have little to do with the coronavirus response.

The administration has defended its spending decisions, saying the Cares Act did not limit how it could spend DPA-related funds, that it had been fully transparent with Congress, and that it had spent the money “to support vital national security industries that were devastated by COVID.”

But the Post’s reporting prompted sharp criticism from Democrats and calls for investigations.

In their Friday letter, the House members requested documents and information on each of the contracts awarded using the relief funds, and on the original decision to use the relief funding to support defense contractors.

A Pentagon spokeswoman, Jessica Maxwell, said the agency had been transparent with lawmakers.

“DOD has done exactly what Congress asked us to do: support American workers, jobs and businesses suffering due to COVID,” she said.