Human smugglers helped the largest single group of migrants across illegally into the U.S. near San Luis, Arizona, earlier this week.
The smugglers tunneled seven holes under the steel border fence — each hole a few feet deep — which allowed the majority of the group to crawl beneath the barrier and into the country Monday, according to U.S. Customs and Border Protection. Some of the Central American migrants managed to climb over the barrier.
"In my 30 years with the Border Patrol, I have not been part of arresting a group of 376 people," Yuma Border Sector Chief Anthony Porvaznik told ABC News. "That's really unheard of."
The group surrendered to Border Patrol agents after crossing the border.
Were there children in the group?
There were 179 children in the group, including 30 unaccompanied minors, according to CBP.
Many migrants bring children because they understand that they won't remain in federal custody if they say they are a family unit.
"Once they're here they know that they're ... not from Mexico, so they can't be returned to Mexico and eventually, they're going to claim asylum," Porvaznik explained.
"The only thing that solves that problem is a change in the law," he continued. "And the reason they're trying to say that they're family units is because they know that if they are a family unit they're going to be released within 20 days."
A Guatemalan man traveling with his 12-year-old daughter said they were headed to San Diego. He already had his plane tickets, according to the report. They had left their home country eight days ago and most of their trip was made by bus.
He said that he had paid a coyote $5,000 to get them across the border quickly. His wife and two younger daughters stayed in Guatemala.
Porvaznik said the agency needs better border barriers and more funding to support those apprehended.
"That's our No. 1 challenge that we have here in the Yuma sector is the humanitarian problem," Porvaznik said. "As I mentioned, 87 percent of the apprehensions here are family units and unaccompanied alien children."
During Monday's apprehension, only three agents were patrolling a 26-mile stretch of the border. The migrants were transported to the central processing center near Yuma.
Another 247 migrants, who crossed illegally in New Mexico, were taken into custody Wednesday.