The Justice Department is investigating whether Minnesota Gov. Tim Walz and Minneapolis Mayor Jacob Frey have impeded federal immigration enforcement through public statements they have made, two people familiar with the matter told the Associated Press.

The investigation focused on potential violation of a conspiracy statute, the people said.

An investigation marks a major escalation in the tense relationship between the state and federal officials over the thousands of immigration agents deployed to Minnesota.

Both DFL officials said in statements that they have not received a notice of an investigation by the DOJ, which can be typical when an official is the target of a federal probe. But they were sharply critical and described it as a stunt.

A Justice Department spokesperson declined to comment.

In a statement, Walz said: “Weaponizing the justice system and threatening political opponents is a dangerous, authoritarian tactic.”

“Two days ago, it was Elissa Slotkin. Last week, it was Jerome Powell. Before that, Mark Kelly,” Walz said, referring to DOJ investigations into two U.S. senators and Powell, the chair of the Federal Reserve. He added that “the only person not being investigated for the shooting of Renee Good is the federal agent who shot her.”

Good was shot Jan. 7 by U.S. Immigration and Customs Enforcement agent Jonathan Ross, sparking citywide protests and calls for a thorough investigation into the use of force.

Within a week, a second shooting involving a federal agent unfolded in north Minneapolis.

Frey said an investigation by the Trump administration is an “obvious attempt to intimidate me for standing up for Minneapolis, our local law enforcement, and our residents against the chaos and danger this administration has brought to our streets.”

“I will not be intimidated,” he said. “My focus will remain where it’s always been: keeping our city safe.”

Republicans have been critical of the Democratic leaders for encouraging people to protest the federal government’s actions.

Some protesters, including Good, have blocked traffic, while others have been violent, including shooting fireworks at law enforcement. Two people were arrested and one charged after vehicles were vandalized and government property was stolen during unrest that followed a federal officer shooting and wounding a man on Jan. 14 in north Minneapolis Both Walz and Frey have urged peaceful demonstrations.

In a primetime address on Jan. 14, Walz urged Minnesotans to “protest loudly, urgently, but also peacefully.” He also said Minnesotans should “peacefully film ICE agents.”

As the Jan. 14 unrest was unfolding, Frey held a news conference in which he scolded violent protesters and urged them to “go home.”

Walz reiterated his past comments again Jan. 16, saying he has “repeatedly, unequivocally, called for peace and a lowering of the temperature,” including in comments made directly to Trump.

The DFL Party chair made similar comments in response to the reported investigation.

“Governor Walz and Mayor Frey have consistently called for calm, peaceful response as ICE continues to conduct chaotic, violent operations in our state,” DFL Party Chair Richard Carlbom said.

CBS News first reported the investigation.

The people with knowledge of the investigation spoke to the Associated Press on condition of anonymity because they were not authorized to discuss it.

Mary Fan, a professor at the University of Washington School of Law, said an investigation or subpoenas aren’t indicators that criminal charges are imminent.

Charges similar to the one reportedly being used are sometimes levied against people who resist arrest, she said. But Fan, a former federal prosecutor, said the charge has also been misused against people who are exercising their First Amendment rights, like recording federal law enforcement agents.

“I think there’s a host of opinions from the lower courts that talk about how you have a right to record the police,” she said.

“Now, if the theory of the case is another allegation that actually incites some sort of assault, that would be a different theory.”

On Friday, Jan. 17, a federal judge prohibited federal immigration agents in Minnesota from arresting, detaining, retaliating against or using force and chemical irritants against “unobstructive protest activity, including observing the activities of Operation Metro Surge.”

Ryan Faircloth and Dave Orrick of the Minnesota Star Tribune contributed to this story. This story contains material from the Associated Press. sarah.nelson@startribune.com