San Luis, Ariz. -- A group of 376 Central Americans was arrested in southwest Arizona, the vast majority of them families who dug short, shallow holes under a barrier to cross the border, authorities said Friday. The group dug under a steel barrier in seven spots about 10 miles east of a border crossing in San Luis and made no effort to elude immigration agents. They included 176 children.

The unusually large group was almost entirely from Guatemala. They were taken to Yuma after entering the country Monday.

"The United States Border Patrol is constantly building intelligence in order to combat these trafficking organizations that are constantly targeting them and gaining intelligence in order to apprehend them in the future," said Jose Garibay, Yuma Sector Border Patrol public information officer, according to CBS affiliate KSWT-TV.

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Customs and Border Protection released photos and video of a long line of migrants standing patiently on a desert road's dirt shoulder after they were stopped. "Almost all were families or unaccompanied juveniles," CPB Arizona said in a tweet.

Pictures of #YumaSector Border Patrol agents processing the group of 376 Central Americans on Monday. #NationalSecurity #SouthwestBorder pic.twitter.com/NxKE2VIeow — CBP Arizona (@CBPArizona) January 18, 2019

Additional footage of #YumaSector Border Patrol agents processing the group of 376 Central Americans on Monday. #NationalSecurity #SouthwestBorder pic.twitter.com/SohiN2XPu0 — CBP Arizona (@CBPArizona) January 18, 2019

The area became a major corridor for illegal crossings in the mid-2000s, prompting the federal government to weld steel plates to a barrier made of steel bollards that had been designed to stop people in vehicles, not on foot, Garibay said. In those spots, there is no concrete footing to prevent digging.

The group used multiple holes in an apparent effort to get everyone across the border quickly, Garibay said.

"In my 30 years with the Border Patrol, I have not been part of arresting a group of 376 people," CBP Yuma Border Sector Chief Anthony Porvaznik told ABC News. "That's really unheard of."

On Wednesday, the Border Patrol arrested a group of 247 people, mostly from Central America, who turned themselves in to agents in a highly remote part of New Mexico, where authorities have found 25 groups of more than 100 people since October. A group of 115 was found in the same area Thursday.

Large numbers of Guatemalan families and unaccompanied children are surrendering to immigration agents in Antelope Wells, New Mexico, where 7-year-old Jakelin Caal and her father were found Dec. 6 with 161 others.

Caal started vomiting on the bus ride to the nearest Border Patrol station 94 miles away and had stopped breathing by the time she arrived. She died at a hospital in El Paso, Texas.

The southwest Arizona desert is less remote but arrests have also sharply increased after years of relative quiet. The Border Patrol's Yuma sector made 7,857 arrests in October and November, more than double the same period a year earlier.

Despite a surge in asylum-seeking families from Central America in recent months, border arrests remain low by historical standards.

The Border Patrol made 396,579 arrests on the Mexican border in the 2018 fiscal year, up 30 percent from a 46-year low during the same period a year earlier but still well below a high of more than 1.6 million in 2000.

Saturday marks the 29th day of the longest government shutdown in history. President Trump and congressional Democrats are currently deadlocked over funding for a border wall. Mr. Trump refuses to sign any government funding bill that does not include money for a wall, and Democrats are refusing to negotiate while the government is shut down. Around 800,000 federal workers have been furloughed or working without pay since the shutdown began.