Arkansas’ removal of thousands of children from Medicaid coverage this year has raised concerns with the U.S. Department of Health and Human Services, according to a Monday letter from the department secretary to Gov. Sarah Huckabee Sanders.

In Arkansas, 78,506 fewer children were enrolled in Medicaid or the Children’s Health Insurance Program (CHIP) in September than in March of this year, an 18% enrollment decrease, according to HHS data.

Much of the decline resulted from the Arkansas Department of Human Services’ six-month review of the eligibility of Medicaid recipients whose coverage was extended for three years due to the COVID-19 pandemic. Roughly 420,000 Arkansans retained coverage during that period even if they no longer qualified for benefits because of income or other eligibility limits.