President Donald Trump’s promised crackdown on illegal immigration has begun to take shape in San Diego County, as federal agents launched targeted operations to arrest undocumented immigrants and a wave of military troops got to work reinforcing U.

The California Highway Patrol on Wednesday issued an Amber Alert for two toddlers who were last seen two days ago in Kings County, north of Bakersfield. Jonathan Maldonado Cruz, 23 — who is considered armed and dangerous — is suspected of taking the 2- and 3-year-old girls named Alana and Arya Maldonado,

The Amber Alert included Los Angeles, Orange, San Diego and Riverside counties, with authorities saying the suspect may have fled to Mexico.

A Border Patrol agent pats down one of four men after the group crossed the border illegally through a gap in two walls separating Mexico from the United States before turning themselves in, Thursday,

A wildfire in the hills near the U.S.-Mexico border exploded early Friday morning over thousands of acres, prompting evacuation orders throughout the Otay Wilderness Area and triggering school closures as well as likely power shutoffs for tens of thousands of people.

After a night of rain that potentially aided firefighting efforts, the Border 2 Fire was 43% contained by Monday morning.

An additional 1,500 troops have arrived at the U.S.-Mexico border after President Donald Trump declared a national emergency in one of his first official acts.

Officials said the fire, which had spread to more than 500 acres by Thursday night, was miles away from threatening any homes or buildings.

Dozens of active duty troops arrived at the U.S.-Mexico border near San Diego on Friday, marking the first batch to deploy following President Donald Trump’s order to bolster border security.

U.S. officials say active duty military troops are arriving in El Paso, Texas, and in San Diego on Thursday evening.

CBS 8 spoke with Cal Fire San Diego on how crews battle fires that happen on the Mexico side of the U.S.-Mexico border.

"It's unprecedented," said Ciudad Juarez municipal official Enrique Licon as workers unloaded long metal bracings from tractor trailers parked in the large empty lot yards from the Rio Grande in order to build a tent city for deportees from the United States.