Images emerged on Wednesday of hundreds of families packed into a grim open air space beneath an underpass, behind razor wire and fencing, their faces – some weary and bewildered, some hopeful – turned toward America.

They are migrants trying to make their way to the United States from Central America and found themselves being held at the US-Mexico border in a parking lot of a border patrol station at the international crossing point in El Paso, in western Texas.

Nearby, the Customs and Border Protection (CBP) commissioner, Kevin McAleenan, declared an “operational crisis” because of a recent surge in the number of people arriving at the border, many hoping to seek asylum, and either crossing into the US unlawfully or waiting in gathering numbers on the Mexican side to be processed.

He said the immigration system on the southern border was at “breaking point” and called on Congress to bring solutions.

McAleenan warned on Wednesday of even longer waits as spring gets under way, and the Trump administration announced it would temporarily reassign 750 border inspectors to address the surge in people arriving in the El Paso area. Most are seeking refuge from violence and poverty, particularly in Honduras, El Salvador and Guatemala, and a new start or a connection with relatives in the US.

Many were crowded into the cramped and dingy parking area beneath the Paso del Norte bridge in El Paso on Wednesday.

Migrants being held for processing under the Paso del Norte bridge in El Paso, Texas, on Wednesday. Photograph: UPI/Barcroft Images

US arrests on the Mexican border jumped to 66,450 in February, up 149% from a year earlier, while arrests in CBP’s El Paso sector, which stretches across New Mexico and much of west Texas, were about eight times higher than they were a year ago, the authorities said.

While arrests are still well below highs of the early 2000s, the surge of families and children has tested both the migrants and the US authorities. Customs and Border Protection is taking more than 60 migrants to the hospital each day, McAleenan said.

CBP has temporarily closed all highway checkpoints along the 268-mile stretch of border in the El Paso sector to try to contain a surge in illegal entry.