As confrontations between federal officers and protesters over a large-scale immigration enforcement operation in Minnesota continued Wednesday, legal and political tensions surrounding the crackdown intensified.

Federal prosecutors have issued grand jury subpoenas to the office of Minnesota Governor Tim Walz and several other state and local officials as part of an investigation into whether they obstructed or interfered with federal law enforcement during immigration operations in the Minneapolis–St. Paul area, according to a person familiar with the matter.

Subpoenas seeking records were also sent to the offices of Attorney General Keith Ellison, Minneapolis Mayor Jacob Frey, St. Paul Mayor Kaohly Her, and officials in Ramsey and Hennepin counties. The source spoke to The Associated Press on condition of anonymity because they were not authorized to discuss an ongoing investigation publicly.

The subpoenas were issued one day after the federal government urged a judge to dismiss a lawsuit seeking to halt the immigration enforcement surge, which has fueled weeks of unrest in Minneapolis and St. Paul. The Justice Department called the state’s legal challenge “without merit.” Ellison has argued that the federal operation violates free speech and other constitutional protections.

Vice President JD Vance is expected to visit Minneapolis on Thursday for a roundtable discussion with local officials and community representatives, according to individuals familiar with the plans. They spoke on condition of anonymity as the trip has not yet been formally announced.

The investigation reportedly centers on whether Minnesota officials obstructed federal immigration enforcement through public statements or directives. Two sources previously said prosecutors are examining potential violations of conspiracy statutes.

A subpoena released by Mayor Frey’s office requests extensive documentation, including any records indicating “a refusal to come to the aid of immigration officials.”

Frey criticized the federal response, saying, “We shouldn’t have to live in a country where people fear federal law enforcement is being used to play politics or silence local voices they disagree with.”