The Pentagon could house as many as 20,000 unaccompanied migrant children on military bases in coming months, after a request by the Department of Health and Human Services, according to a Pentagon spokesman.

“The Department of Defense has received a request for assistance from the Department of Health and Human Services (HHS). HHS has requested DOD to determine its capabilities to provide up to 20,000 temporary beds for unaccompanied alien children at DOD installations,” said Pentagon spokesman Air Force Lt. Col. Michael Andrews.

He said that while four bases have been visited by HHS for possible housing, it does not mean that children will be housed there.

“HHS and DOD are working closely to determine the requirements and timing for support.  Secretary Mattis’ guidance has been clear: that the DoD will support our federal partners,” Andrews said.

If approved, it would not be the first time unaccompanied migrant children are housed at military bases.

In 2014, the Obama administration approved a plan to house 7,000 unaccompanied migrant children on three military bases: Lackland Air Force Base in Texas, Fort Sill in Oklahoma, and Naval Base Ventura County in California.

According to a notification to lawmakers from the Pentagon first reported by the Washington Post, officials at HHS asked whether the beds could be provided for children for July through December 31. HHS would reimburse the DOD for costs. The sites will be run by HHS employees or contractors, who will provide care and supervision for the children.

The request from HHS comes after President Trump ordered Defense Secretary Jim Mattis to provide the Department of Homeland Security with existing facilities to house and care for “alien families” and construct new facilities “if necessary and consistent with law.”

HHS officials have visited four bases in recent weeks: Fort Bliss, Dyess Air Force Base, Goodfellow Air Force Base in Texas, and Little Rock Air Force Base in Arkansas.

Mattis said Wednesday that the Pentagon would comply with any request made by the White House.

“We have housed refugees,” he said. “We have housed people thrown out of their homes by earthquakes and hurricanes. We do whatever is in the best interest of the country.”