MCALLEN, Texas — Seconds after the radio crackled and the government SUVs sped into the darkness, Border Patrol agents sprinted through the brush and toward the border in an all-too-familiar pursuit of drug smugglers.

"They dropped their bundles of narcotics and went back into Mexico," said agent Marlene Castro, sounding disappointed after racing through a pitch-black clearing outside Rio Grande City. Still, on this recent night, agents would recover 66 pounds of marijuana with a street value of roughly $53,000.

But chasing drug smugglers wasn't the only thing keeping them busy.

During two days that NBC News spent with U.S. Customs and Border Protection officials, it became clear that Castro and her colleagues were dealing with a sudden surge of families from Central America who are running toward those officials — not from them.

Many of the families are eager to be caught so they can apply for asylum or temporary protected status as they try to escape the violence back home.

Apprehensions on the Southwest border, along the Rio Grande, are rising. There were 46,195 in October — that was almost 20,000 more than the same month two years ago and the largest spike since the massive surge of unaccompanied minors during the summer of 2014.

Castro said the biggest difference this time around is that the Border Patrol is better equipped to deal with the influx. A new processing center has the capacity to hold 1,000 migrants at a time. In November, the federal government even sent 150 more border patrol agents to the McAllen area in the southern tip of Texas.

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