The U.S. Department of Labor is suing a Texas state agency for more than $1 million in unpaid overtime, claiming that hundreds of child welfare employees worked off the clock and were instructed not to record all their hours.

The federal agency filed the lawsuit Wednesday against the Texas Department of Family and Protective Services and its Child Protective Services Division in Austin. The suit claims 800 current and former investigators and case workers with CPS were denied proper overtime compensation.

The department investigated a three-year period after a complaint was filed in U.S. District Court of the Western District of Texas.