Maine Secretary of State Shenna Bellows said Wednesday her department will continue to hold off on giving out undercover license plates to federal law enforcement agents.

“We are not issuing unmarked plates to federal agencies until we receive further assurances that Maine plates won’t be used for lawless purposes,” Bellows said in an interview Wednesday. “I have deep concerns that what is happening right now in our communities violates the Constitution and established law.”

Bellows’ comments came days after the the Bureau of Motor Vehicles, housed in the secretary of state’s office, denied a request from U.S. Customs and Border Protection for confidential, undercover plates.

The request came amid rumors that federal authorities would be ramping up immigration enforcement activities. Bellows, who is running for governor as a Democrat, said Saturday that “abuses of power” by immigration agents in Minnesota and elsewhere in the U.S. prompted her department’s action.

Officials with the U.S. Department of Homeland Security confirmed Wednesday they are working on an operation in Maine “to target the worst of the worst criminal illegal aliens in the state.” An administration official said 50 people were arrested Tuesday.

Unmarked vehicles are permitted in Maine for law enforcement purposes with authorization from the secretary of state.

Other federal agencies have also requested the plates, but Bellows said she could not name those departments because such requests are confidential under the law.

A pause on the issuance of new plates is unprecedented under Bellows’ tenure, which began in 2021. She said she could not say whether past secretaries of state have ever taken such an action.

The pause does not apply to local and state law enforcement. It’s unclear how many federal agencies are being impacted.

An official with the U.S. Marshals Service, which serves as the enforcement and security arm of the judicial branch, said Saturday it was unable to renew undercover registrations for a number of vehicles last week, raising safety concerns for the agency.

Asked Wednesday why the pause has been applied across federal agencies and not limited to those dealing specifically with immigration, Bellows said “we have seen federal authorities from a variety of agencies engaging in very concerning activities in Minnesota.”

Minnesota is also in the midst of a surge in U.S. Immigration and Customs Enforcement activity.

Ryan Guay, a supervisory deputy U.S. marshal for the U.S. Marshals Service District of Maine, did not respond to a phone message or email Wednesday afternoon seeking comment.

Spokespeople for U.S. Customs and Border Protection did not immediately respond to emails seeking information about the use of the plates, and how not having them will affect operations.

Bellows said Wednesday that her office has been accused of publishing law enforcement addresses and identities as part of their decision, but she said that is not the case. The license plates in question are registered to agencies, not individual officers.

“We would never dox a member of law enforcement,” she said. “Their safety is really important to us.”