The US Justice Department has opened an investigation into whether Minnesota Governor Tim Walz and Minneapolis Mayor Jacob Frey obstructed federal immigration enforcement through public statements made during an aggressive Immigration and Customs Enforcement (ICE) operation in the Twin Cities, according to officials familiar with the matter.

The probe is examining potential violations of a federal conspiracy statute and comes amid one of the largest immigration enforcement operations ever conducted in Minneapolis and St. Paul. The Department of Homeland Security says the weeks-long operation has resulted in more than 2,500 arrests.

Governor Walz has strongly criticised reports of the investigation, calling it an example of the justice system being weaponised against political opponents. His office said it has not received any formal notice from the Justice Department. Mayor Frey’s office did not immediately respond to requests for comment.

Tensions have been rising since the fatal shooting of Renee Good on January 7 during an ICE-related incident, which intensified protests across the region. State and local leaders have repeatedly urged demonstrators to remain peaceful as federal agents used tear gas and flash-bang devices to control crowds.

The crackdown has also drawn attention to controversial arrests, including that of Garrison Gibson, a Liberian national who was detained, released by a federal judge, re-arrested during a routine immigration check-in, and then released again hours later after ICE acknowledged procedural errors.

Amid growing fear in affected communities, Native American leaders have urged tribal members to carry identification after reports of ICE agents stopping or detaining Indigenous people. Democratic lawmakers and local officials have also reported concerns from residents, including claims of agents going door to door in immigrant neighbourhoods.

The investigation unfolds as President Donald Trump has threatened — and later softened — the possibility of invoking the Insurrection Act to deploy troops if protests escalate, underscoring the volatile political and legal battle surrounding the federal immigration operation in Minnesota.