The temporary camp in Del Rio has grown with staggering speed in recent days during a massive surge in migration that has overwhelmed the authorities.

The men showed up unannounced, but it didn’t take long for Aleida Flores Garcia to figure out why they were measuring portions of her backyard. “We are here to mark where a border wall would go,” they told her last summer as they surveyed the ranch her family has owned for five generations.

“Texas will not sit idly by as this crisis grows,” Gov. Greg Abbott said of border crossings, while offering few details about the wall.