More than 330 unaccompanied migrant children are inside the U.S. Customs and Border Protection migrant facility in Donna waiting to be processed.

In a visit to the facility, Secretary of Homeland Security Alejandro Mayorkas said the number is a dramatic decrease compared to the more than 3,700 unaccompanied children who were there in April.

"The challenge remains.” Secretary Mayorkas said. “It is not behind us, but our plan of execution is well underway and the results are compelling."

Federal agents said back in April, children would wait in cramped, overcrowded holding rooms for about five days for processing. The average wait time is currently down to about 26 hours. 

Officials say a slight decrease of migrants crossing the border and more efficiently transferring children to health and human services plays a role in lower numbers 

In light of the reduced numbers, federal agents are spending $19 million constructing another holding tent in the facility. 

“We must maintain the capacity to deal with and address the dynamism so we do not experience to the best of our abilities what we experienced at the end of March and the beginning of April,” Mayorkas said. 

According to Mayorkas, the border remains closed and DHS is moving forward with Operation Sentinel to address putting an end to the business of human smuggling that exploits vulnerable children and families.