One of the largest U.S. labor unions asked a federal judge on Wednesday to block Elon Musk's government cost-cutting effort from accessing the Department of Labor's systems, which the union warned could give the billionaire sensitive information about investigations into his companies.

Elon Musk's Department of Government Efficiency representatives are at the Centers for Medicare & Medicaid Services this week examining payment and contracting systems of federal health agency. Two senior agency veterans focused on policy and operations are working with DOGE to review the agency overseeing Medicare and Medicaid,