Gov. Tim Walz invited President Trump to come to Minnesota and "see our values in action," as the U.S. Department of Justice served his office and the offices of several other state officials with subpoenas as part of an investigation into an alleged conspiracy to impede federal immigration agents.

Walz's office was served subpoenas along with the offices of Minneapolis Mayor Jacob Frey and Attorney General Keith Ellison Tuesday afternoon. Justice Department officials also subpoenaed the offices of St. Paul Mayor Kaohly Her and officials in Ramsey County and Hennepin County, sources told CBS News.

Multiple sources familiar with the matter told CBS News last week that the Justice Department was investigating Walz and Frey for their public comments about the thousands of federal agents deployed to the Minneapolis area in recent weeks. The governor and mayor have both demanded U.S. Immigration and Customs Enforcement leave the state after one of its agents shot and killed Renee Good earlier this month.

"Mr. President, Minnesota invites you to see our values in action. Come see how communities from all walks of life are working together, and how the spirit of this state refuses to be defined by division or fear," Walz wrote on social media. "I invite you to join me, and others in our community, to help restore calm and order and reaffirm that true public safety comes from shared purpose, trust, and respect. 

He added that "The state of Minnesota will not be drawn into political theater" and blasted the DOJ's investigation as a "partisan distraction." 

A Justice Department spokesperson declined to comment on the investigation. 

Frey's office said that "when the federal government weaponizes its power to try to intimidate local leaders for doing their jobs, every American should be concerned," adding that he'll continue to work as mayor to keep the Minneapolis community safe. 

Her's office released the following statement Tuesday afternoon: "The president promised retribution, and consistent with that promise, we received a subpoena today from the US Attorney's Office. I am unfazed by these tactics, and I stand firm in my commitment to protect our residents, neighbors, and community."

An estimated 3,000 federal agents have swarmed into Minnesota since early December, and officials said they have made thousands of arrests. Local authorities and the public have accused ICE and Border Patrol agents of constitutional violations.

The federal inquiry is focused on a federal statute, 18 U.S.C. § 372, one U.S. official told CBS News, which makes it a crime for two or more people to conspire to prevent federal officers from carrying out their official duties through "force, intimidation or threats."

The statute has historically been used in cases involving coordinated efforts to obstruct federal officials, including actions involving violence or threats. Public criticism of federal policy has historically been treated as protected speech unless involving direct coordination or incitement to obstruct law enforcement.

Justice Department wages multiple legal battles in Minnesota

The investigation is one of several legal battles the DOJ is fighting in Minnesota.

On Monday, the department filed a memorandum — as required by the judge — arguing against a motion filed by the state of Minnesota, Minneapolis and St. Paul for a temporary injunction to stop the surge of federal agents. The lawsuit, filed late last week, argues the influx is endangering citizens and accuses ICE of violating the First and 10th amendments. The DOJ called the claims "legally frivolous" and asked for the judge to deny the motion.

Days earlier, the same judge blocked federal agents in the state from using pepper spray or nonlethal munitions on, or arresting, peaceful protesters. U.S. District Judge Katherine Menendez's order also bars federal law enforcement from stopping or detaining drivers and passengers when there is "no reasonable articulable suspicion" that people driving near protests are forcibly interfering with law enforcement operations. Department of Homeland Security Secretary Kristi Noem called the order "a little ridiculous," and the Justice Department plans to appeal.

The DOJ is also investigating a group of protesters who disrupted services at a St. Paul church, the pastor of which apparently also leads the local ICE field office.

Last week, at least six prosecutors resigned from the U.S. Attorney's Office in Minnesota, which is overseen by the DOJ. Two sources told CBS News the resignations resulted from concern over a request to probe Good's widow and the handling of the investigation as an assault on a federal officer instead of a civil rights case.