The Justice Department sent subpoenas to Minnesota Gov. Tim Walz, Minneapolis Mayor Jacob Frey and other local officials, as part of a widening investigation into whether state leaders conspired to impede law enforcement during the Trump administration's immigration operations, according to a document reviewed by NBC News and a person familiar with the investigation.

The subpoenas were also sent to Minnesota Attorney General Keith Ellison and the office of St. Paul Mayor Kaohly Her, and two counties, according to the document and the person familiar with the probe.