Gerston Miranda and his wife were among thousands of migrants recently arriving at this remote area on Arizona’s southern border with Mexico, squeezing into the United States through a gap in the wall and walking overnight about 14 miles (23 kilometers) with two school-aged daughters to surrender to Border Patrol agents.

“There is no security in my country,” said the 28-year-old from Ecuador, who lost work when his employer closed due to extortion by criminals. “Without security you cannot work. You cannot live.”

A shift in smuggling routes has brought an influx of migrants here from countries as diverse as Senegal, Bangladesh and China, prompting the Border Patrol to seek help from other federal agencies and drawing scrutiny to an issue critical in next year’s presidential elections.

With hundreds of migrants crossing daily in the area, the U.S. government on Monday indefinitely shut down the nearby international crossing between Lukeville, Arizona, and Sonoyta, Mexico, to free Customs and Border Protection officers assigned to the port of entry to help with transportation and other support. The agency also has partially closed a few other border ports of entry in recent months, including a pedestrian crossing in San Diego and a bridge in Eagle Pass, Texas.