Three Republican senators have sent a letter to the Centers for Medicare and Medicaid Services expressing concern for the “lack of oversight for more than $1 billion in federal grants” given to state-based marketplaces.

In the letter to CMS Acting Administrator Andy Slavitt, the senators — Orrin Hatch of Utah, Chuck Grassley of Iowa, and John Barrasso of Wyoming — note a handful of state-based exchanges have switched to the federal marketplace, run by CMS, and inquire if the agency will seek reimbursement for funds the states received from CMS to set up a state-based marketplace.