The federal government plans to place as many as 1,400 unaccompanied migrant children in makeshift housing on the Fort Sill Army installation in Oklahoma, officials announced Tuesday.

The Office of Refugee Resettlement (ORR) is required by law to provide shelter, health care and other services for migrant children who are either apprehended alone or with anyone other than their own parents, but the agency is grappling with an unexpected surge in such children. As a result, officials say the agency's more than 167 shelters across the country could be insufficient to house what it's calling an "influx" of children.

According to agency statistics, ORR took in 40,900 children during the first seven months of the current fiscal year, an increase of 57% from last year.

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Last week, officials toured vacant buildings on several military bases, including Fort Benning in Georgia, and the Malmstrom Air Force Base in Montana. However, the agency said in a statement Tuesday that those facilities are no longer available. It is not clear what they will now be used for.

The agency said in its statement that the Fort Sill location was previously used to house unaccompanied children briefly in 2014.

"After assessing the property staff determined the site meets the standards for (unaccompanied migrant child) operations," the agency said. "Fort Sill served as a temporary emergency influx shelter for UAC in 2014 as a result of a migration surge at that time."

In addition to Fort Sill — which during World War II was used as an internment camp for Americans of Japanese descent — the agency said in its statement that it is also considering placing another large-scale facility for unaccompanied migrant children at the Santa Teresa Land Port of Entry in New Mexico.

The moves come as Congress considers a request by the U.S. Department of Health and Services, which operates ORR, for an emergency infusion of nearly $2.9 billion. The agency says it is in dire financial straits as a result of the "influx," and as a result, it has since begun cutting all but essential services for children.

HHS confirmed to CBS News last week that it is not offering the majority of education, legal services and recreation that it is required to provide children in its custody. Spokesperson Mark Weber said that the agency is also required by law to do so during a budget crisis.

"Given that we know that we are going to run out of funding, we are required to take some steps required by the Antideficiency Act, and that means scaling back funding for things like education, lawyers, recreational activities that are not essential to protecting life and property," Weber said.

The Fort Sill site will be the second location out of more than 160 shelters nationwide to be located on federal land, and as a result it will not be subject to state child welfare inspections. The only other site not overseen by state authorities is the nation's largest such facility, in Homestead, Florida.