The number of immigrant children being held in government custody has reached almost 15,000, putting a network of federally contracted shelters across the country near capacity.

The national network of more than 100 shelters is 92 percent full, according to the Department of Health and Human Services. The situation is forcing the government to consider a range of options, possibly including releasing children more quickly to sponsors in the United States or expanding the already crowded shelter network.

Most of the migrant children are teenage boys from Central America who travel to the border alone. Many are escaping poverty or gangs, and they plan to ask for asylum and ultimately find work or go to school in the U.S.

Waves of these so-called unaccompanied children have arrived in recent years, and the numbers are on the rise again. In November, according to Customs and Border Protection, an average of 175 unaccompanied children crossed the southern border every day.

The largest migrant youth shelter in the country is in Tornillo in remote west Texas. About 2,800 children live in heated, sand-colored tents set up on a patch of desert a few hundred yards from the Rio Grande.