The US Department of Homeland Security (DHS) on Friday gutted three oversight offices by placing more than 100 workers on paid leave, a Trump administration official and two former officials said.

The workers, including those in the DHS Office for Civil Rights and Civil Liberties, were given layoff notices as part of a large-scale government reduction by the Trump administration, one of the affected staffers said, requesting anonymity to discuss the matter.

“These offices have obstructed immigration enforcement by adding bureaucratic hurdles and undermining DHS’s mission,” DHS spokesperson Tricia McLaughlin said in a statement. “Rather than supporting law enforcement efforts, they often function as internal adversaries that slow down operations.“

McLaughlin said the offices would be subject to a “reduction in force”, the government term for layoffs.

Trump launched a wide-ranging immigration crackdown after taking office on 20 January, pulling resources from across the federal government to focus on enforcement. Advocates have raised concerns that the more aggressive efforts could infringe on the rights of immigrants and US citizens alike.

White House officials are reviewing federal agencies’ downsizing plans, a move expected to result in the mass firing of thousands of government workers within the coming weeks, Reuters reported on Friday.

Trump had given the agencies until 13 March to draw up plans for a second wave of mass layoffs as part of his rapid-fire effort to reshape and reduce the size of the federal government, which he has called bloated and inefficient.

The DHS Office for Civil Rights and Civil Liberties investigates potential rights violations within the department and fields complaints from the public.

The other two offices targeted were the Office of the Citizenship and Immigration Services Ombudsman and the Office of the Immigration Detention Ombudsman, which served similar oversight functions.

Thousands of workers fired in Trump’s effort to slash the government workforce have sued to have their jobs reinstated by federal judges.