Immigrant rights groups were outraged on Friday as reports surfaced that the Trump administration is considering a proposal to separate immigrant families who attempt to cross the U.S.-Mexico border—crossing a line that previous administrations have stopped short of even as they have attempted to cut down on immigration.

Families have generally been allowed to stay together in family detention centers under the current policy. The new proposal would see parents sent to adult facilities after being apprehended at the border while their children would be sent to juvenile shelters.

Undocumented immigrants living in the U.S. would also be singled out for deportation if they attempt to retrieve their children from detention centers, under the new rules.

Immigration and Customs Enforcement (ICE) officials have approved the plan, but Homeland Security Secretary Kirstjen Nielsen has yet to sign off. John Kelly, who previously headed President Donald Trump’s Department of Homeland Security (DHS) and now serves as his chief of staff, pushed the idea earlier this year, but the administration backed off the plan due to a sharp decline in immigration after Trump entered office.

More than 29,000 people were apprehended by border patrol agents in November, up from about 11,000 in April.

Immigration advocates note that the proposal would be making official a practice that has already been in play along the border. Earlier this month, eight groups including the Immigration Justice Campaign filed a complaint regarding ICE’s forcible separation of at least 150 immigrant families, some of whom had children as young as a year old.