The Justice Department announced this week that it plans to end its use of private prisons.

According to the Washington Post, officials concluded the facilities are both less safe and less effective at providing correctional services than those run by the government.

Deputy Attorney General Sally Yates made the announcement on Thursday (Aug. 17), via a memo that instructs officials to either decline to renew the contracts for private prison operators when they expire or “substantially reduce” the contracts’ scope.

The goal, according to Yates, is “reducing — and ultimately ending — our use of privately operated prisons.”

“They simply do not provide the same level of correctional services, programs, and resources; they do not save substantially on costs; and as noted in a recent report by the Department’s Office of Inspector General, they do not maintain the same level of safety and security,” Yates wrote.

Yates says there are 13 privately run facilities in the Bureau of Prisons system, but they won’t close overnight. The Justice Department will instead review existing contracts that come up for renewal.

Since the news surfaced, shares of two major prison companies plunged, down by more than 40% by midday.