McAllen, --

Texas - An unprecedented surge of children caught trudging through southern Texas scrublands or crossing at border ports of entry without their families has sent government and nonprofit agencies scrambling to expand their shelter, legal representation and reunification services. On any given day this year, the U.S. Office of Refugee Resettlement has been caring for more than 2,100 unaccompanied child immigrants.

The influx came to light recently when 100 kids were taken to Lackland Air Force Base near San Antonio for temporary housing. It was the first time the government has turned to the Defense Department - in all, 200 boys and girls younger than 18 stay in a base dormitory.

While the issue of unaccompanied minors arriving in the United States isn't new, the scale of the recent increase is. From October through March, 5,252 kids landed in U.S. custody without a parent or guardian - a 93 percent increase from the same period the previous year, according to data released by the Department of Health and Human Services. In March alone, 1,390 kids arrived.

"The whole community right now is in triage mode," said Wendy Young, executive director of Kids in Need of Defense, a Washington nonprofit that matches pro bono attorneys with minors navigating the immigration system.

Unaccompanied children are first processed by the Department of Homeland Security and then turned over to the Office of Refugee Resettlement while the deportation process begins. Once in a shelter, the search begins for their relatives or an acceptable custodian. When a custodian is found, the child can leave the shelter and await immigration proceedings.

The cause of the surge remains a mystery to child migrant advocates and government officials. The kids are coming from the same places as usual - Guatemala, El Salvador, Honduras and Mexico - and they offer the same range of explanations: They made the trek to look for parents already in the United States; they're seeking economic opportunity to send money home; they want to escape violence or abuse.

"We're talking to the children, but we don't have one solid answer," Fisher said. "There seem to be the same reasons that we've seen before."