WASHINGTON — The Trump administration is reassigning at least half the top leadership at Immigration and Customs Enforcement offices around the country in a major shake-up of the agency responsible for carrying out the president’s vision for mass deportations, according to one current and one former U.S. government official. The current official, who was not authorized to speak publicly on the matter and spoke on condition of anonymity, said 12 ICE field office directors — the officers who run the network of field offices around the country responsible for immigration enforcement — were being reassigned.

Half are to be replaced by existing or retired Customs and Border Protection staff, while the other half would be replaced by ICE officers, both the current and former officials said. The changes were initiated by the Homeland Security Department, the current official said, without specifying which cities were impacted.

The former official, who has direct knowledge of the changes and spoke on condition of anonymity to discuss information that was not intended for public release, said on top of the 12 reassignments, leaders in another four cities were being swapped out through retirements or other circumstances. He said the cities include major immigration enforcement targets such as Chicago, Los Angeles and Washington.

He added that ICE leadership has been discussing the changes with other Trump administration officials for some time as part of a broad review of the agency.

The reason for the personnel changes wasn’t immediately clear. But they indicate a greater integration of Border Patrol agents in ICE at a time when Customs and Border Protection has been accused of using heavy-handed tactics in its immigration enforcement.

With a total of 25 field offices around the country, the reassignments amount to turnover of about half or more of the top staffers carrying out the president’s hardline immigration enforcement plans, which has seen a major deployment of law enforcement in major American cities, thousands of arrests and surging fear among residents, especially in immigrant communities.