The Department of Health and Human Services is allowing members of Congress to visit a Texas immigration detention center amid growing concerns about access to such facilities housing the recent surge of children who have illegally crossed the U.S.-Mexico border.

The tour is scheduled to take place Tuesday morning. The site will be a temporary shelter at the Joint Base San Antonio Lackland, according to The Blaze news website.

Tens of thousands of young people -- including an estimated 50,000 children -- have illegally crossed the border in recent months, sent by their parents to escape violence in Central America and connect with relatives in the United States.

The long-simmering issue about what the U.S. should do with an estimated 11.5 million people now living here illegally and the need to tighten border security has emerged as a key 2014 election issue. The surge of illegals also resulted this week in a tense standoff in Southern California in which residents of the city of Murrieta turned back buses carrying an overflow of illegal border-crossers.

Lawmakers are also concerned about the children’s exposure to disease and physical attacks during their long journeys.

The debate in Washington about which political party is to blame could hit a political high note next week when President Obama is expected to ask Congress for $2 billion to help with the border-crossing crisis.

Republicans blame Obama for a 2012 executive orders that made some young illegal immigrants eligible for deferred deportation. Democrats blame the GOP-led House for not voting on immigration-reform legislation.

Members of Congress have already been invited in recent weeks to visit facilities, including a June 12 offer to see the one at the Ventura County Naval Base in Oxnard, Calif. And House Minority Leader Nancy Pelosi, D-Calif., is scheduled Saturday to go to the South Texas Detention Center, in Pearsall.

However, Oklahoma GOP Rep. Jim Bridenstine said Wednesday that he was recently denied access to Fort Sill, one of three U.S. facilities housing the unaccompanied children, and was told the soonest he could get in was July 21.

“Any member of Congress should have the legal authority to visit a federal youth detention facility without waiting three weeks," he said. “What are they trying to hide? As a Navy pilot, I have been involved in operations countering illicit human trafficking. I would like to know to whom these children are being released."

As with the previous tours, the HHS has issues rules for the Lackland, Texas, tour that includes no recording devices, no interacting with staffers and the children and no questions until after the tour.