Department of Corrections secretary Mike Crews is threatening to stop payments to a Missouri-based company that won a five-year, $1.2 billion contract to provide health care to the majority of the state’s prisoners, accusing Corizon of failing to provide adequate treatment.

Crews sent a letter to Corizon CEO Woodrow Meyers on Friday saying that the company has failed to follow through after audits revealed shortcomings in multiple areas, including medical care, nursing and administration.