MINNEAPOLIS — Federal prosecutors served grand jury subpoenas Tuesday to Minnesota officials as part of an investigation into whether they obstructed or impeded law enforcement during a sweeping immigration operation in the Minneapolis-St. Paul area, a person familiar with the matter said.

The subpoenas, which seek records, were sent to the offices of Gov. Tim Walz, Attorney General Keith Ellison, Minneapolis Mayor Jacob Frey, St. Paul Mayor Kaohly Her and officials in Ramsey and Hennepin counties, the person said.

The person was not authorized to publicly discuss an ongoing investigation and spoke to The Associated Press on condition of anonymity.

The subpoenas are related to an investigation into whether Minnesota officials obstructed federal immigration enforcement through public statements they made, two people familiar with the matter said Friday. They said then that it was focused on the potential violation of a conspiracy statute.

Walz and Frey, both Democrats, have called the probe a bullying tactic meant to quell political opposition. Frey’s office released a subpoena, which requires a long list of documents for a grand jury on Feb. 3, including “any records tending to show a refusal to come to the aid of immigration officials.”

“We shouldn’t have to live in a country where people fear that federal law enforcement will be used to play politics or crack down on local voices they disagree with,” Frey said.

Her, a Hmong immigrant and a Democrat, also acknowledged a subpoena, saying she’s “unfazed by these tactics.” The governor’s office referred reporters to a statement earlier Tuesday in which Walz said the Trump administration was not seeking justice, only creating distractions.

The subpoenas came a day after the government urged a judge to reject efforts to stop the immigration enforcement surge that has roiled Minneapolis and St. Paul for weeks.

The Justice Department called the state’s lawsuit, filed soon after the fatal shooting of Renee Nicole Good by an immigration officer, “legally frivolous.”

“Put simply, Minnesota wants a veto over federal law enforcement,” government attorneys wrote.

Ellison said the government is violating free speech and other constitutional rights. He described the armed officers as poorly trained and said the “invasion” must cease. It’s not known when U.S. District Judge Katherine Menendez will make a decision.

Ilan Wurman, who teaches constitutional law at University of Minnesota Law School, doubts the state’s arguments will be successful. He said immigration enforcement is clearly a matter of federal control.

Greg Bovino of U.S. Border Patrol, who has commanded the Trump administration’s big-city immigration crackdown, said more than 10,000 people in the U.S. illegally have been arrested in Minnesota in the past year, including 3,000 “of some of the most dangerous offenders” in the last six weeks during Operation Metro Surge.

He highlighted the capture of three people with criminal records from Laos, Guatemala and Honduras.

“These are not technical violations. As I mentioned, these are individuals responsible for serious harm,” Bovino said at a news conference.

Julia Decker, policy director at the Immigrant Law Center of Minnesota, expressed frustration that advocates have no way of knowing whether the government’s arrest numbers and descriptions of the people in custody are accurate.

“These are real people we’re talking about, that we potentially have no idea what is happening to them,” Decker said.