ST. PAUL, Minn. (AP) — The Minnesota Department of Human Services says it underestimated the amount of money it overpaid two Native American tribes for substance abuse treatment covered under Medicaid.

The agency reported last month that it overpaid the Leech Lake Band of Ojibwe and the White Earth Nation by more than $25 million. The Pioneer Press reports that officials on Tuesday revised that figure to about $29 million.

The overpayments occurred because the tribes were told they could bill for drug treatment medication that patients took at home. The agency now says those treatments are not eligible for reimbursements and it owes the federal government for five years of overpayments.

In addition, Human Services must pay back another $48 million that it improperly distributed to certain state chemical dependency treatment providers.