House Republicans subpoenaed the White House for documents surrounding billion-dollar payments to insurers under Obamacare.

Key committee leaders said Wednesday they were tired of waiting for answers on the law's cost-sharing reduction program. Members of the House Energy and Commerce and Ways and Means committees are concerned that the Obama administration is giving insurers subsidies that weren't appropriated by Congress.

We've gone above and beyond to give the administration every opportunity to comply with our repeated requests for details," said Reps. Fred Upton, R-Mich., and Kevin Brady, R-Texas. "Now, 15 months after our first request, we still don't have the most basic information about the $5 billion in unlawful payments to insurance companies."

Upton leads Energy and Commerce, while Brady helms Ways and Means.

The cost-sharing program was created to help lower the prices of insurance plans offered on Obamacare. The government can pay back insurers to offset the low prices.

But the lawmakers charge that the subsidies were never fully appropriated by Congress.

The charge is also the focal point of a lawsuit from the House against Obamacare, which is pending in the lower courts.

The two House members said they first requested documents in February 2015 and pressed for the documents until December 2015.

That month the administration sent a joint response but committee members said it wasn't enough.

In January, the committees subpoenaed the Department of the Treasury for documents related to the request. In March, the Department of Health and Human Services produced documents for the committees and a high-ranking official for a briefing.

However, the committees said the documents were already publically available. The interview of Health and Human Services official Ellen Murray was hindered as HHS counsel wouldn't allow her to "answer questions posed by committee staff about the decision to fund the cost-sharing reduction program with funds appropriated to other programs," the commitee said.

The committees added that in March, HHS produced one other document, but the lawmakers weren't satisfied.

The subpoenas call on HHS to issue the documents by May 18.