About 150 Border Patrol agents will be deployed to South Texas from Arizona, California and elsewhere to help process a spike in immigrants who have been apprehended after illegally entering the U.S., federal officials announced Saturday.

Agents from Tucson, Arizona, and San Diego will be temporarily reassigned to the Rio Grande Valley, and agents working another portion of the Texas border will join them, U.S. Customs and BorderProtection said in a statement.

The additional agents will assist with screening and processing immigrants taken into custody along the border, many of whom are unaccompanied children and families.

Hundreds of thousands of people have sought asylum along the U.S.-Mexico border in the last two years, and the majority are Central American families who often turn themselves in as opposed to mostly Mexican men trying to evade capture, according to a federal report obtained last month by The Associated Press.

Since 2014, the Rio Grande Valley has led the nation as the region with the most apprehensions of immigrants entering the U.S. illegally. Asylum seekers, many of them fleeing drug-fueled violence south of the border, peaked in 2014 at 170,000, nearly triple the 63,000 who arrived the previous year. Before 2012, there were fewer than 30,000 a year.

Leaders in the South Texas city of McAllen said earlier this month that they're struggling to provide services and noted that October was the busiest month since 2014 for a church support center, with more than 5,600 immigrants offered assistance. The city and local groups have spent nearly $1 million over two years to provide showers, tents and other needs, Mayor Jim Darling told The Monitor newspaper.

U.S. Department of Homeland Security Secretary Jeh Johnson said in a statement Thursday there are about 41,000 people being held in U.S. immigration detention facilities. The number normally fluctuates between 31,000 and 34,000, he said.

"Our borders cannot be open to illegal migration," Johnson said. "We must, therefore, enforce the immigration laws consistent with our priorities. Those priorities are public safety and border security. Specifically, we prioritize the deportation of undocumented immigrants who are convicted of serious crimes and those apprehended at the border attempting to enter the country illegally."