The idea was meant to supercharge President Trump’s mass deportation plan.

Immigration and Customs Enforcement would purchase more than a dozen empty warehouses across the United States to massively expand its capacity to detain people deemed to be in the country illegally, which in turn would spike deportations. A year into Mr. Trump’s term, it had bought 11 facilities at a cost of $1 billion.

But in a major turnabout, the agency is planning to offload seven warehouses purchased for more than $700 million by either giving them to other federal agencies or selling them outright, according to documents obtained by The New York Times.

The decision to sharply scale back the warehouse plan is a rejection of a signature initiative under the previous homeland security secretary, Kristi Noem, who pushed the boundaries of what the government can do to aggressively round up potential deportees. The new secretary, Markwayne Mullin, who had privately expressed skepticism about the plan, has said publicly that he wants the agency to be quieter about how it carries out immigration enforcement.

“From Day 1, D.H.S. has remained singularly focused on removing the worst of the worst criminal illegal aliens from the United States and is always evaluating the best methods to do so,” the Homeland Security Department said in a statement for this article. “These heinous criminals, once arrested, should be removed at lightning speed, not housed on American soil at the taxpayer’s expense. D.H.S. is moving swiftly to utilize EXISTING detention space with our state and county partners.”