ST. PAUL, Minn. (AP) _ New revelations about overpayments to two American Indian tribes are bringing more scrutiny to Minnesota's Department of Human Services.

Reports say the department overpaid the Leech Lake Band of Ojibwe and the White Earth Nation by $25.3 million for substance abuse treatments covered by Medicaid. The newspaper cited internal memos.

The $25.3 million in overpayments is a preliminary estimate. The memo does not explain how it happened.

Democratic Gov. Tim Walz says the overpayments occurred over the past five years, before he took office in January. Walz says the payment structure was corrected in May.
Legislative Auditor James Nobles says he is launching an investigation into the overpayments.

The Human Services Department has been hit by turmoil, with Commissioner Tony Lourey abruptly resigning last month.