SAN DIEGO -- An Immigration and Customs Enforcement program focusing on catching illegal immigrants with a criminal history is proving to be effective, 10News reported.

Authorities said an estimated 12 million people are living in the U.S. illegally, with many having crossed borders to enter the country. Law enforcement agencies said they just don't have the manpower to go after each person, so they're refocusing their efforts

"We're gonna go after them. We're gonna find them. We're going to take them into custody and remove them from the country," said Robin Baker, Director of ICE in San Diego.

Baker said limited resources, compared to the high number of illegal immigrants living in the U.S., have prompted his agency to prioritize.

"In 2008, we just tried to get as many fugitives as we could. Now, we're trying to get as many fugitives as we can; we just want them to be criminals," said Baker.

In an effort to be efficient, Baker said ICE agents across the country have begun focusing on illegal immigrants with a criminal history, including murderers, rapists and armed robbers.

In the last few months, three undercover teams have been patrolling the streets of San Diego County searching for clues that could lead to an arrest. Baker said the undercover work along with a closer relationship with law enforcement has proven successful, and numbers obtained by 10News seemed to back that claim.

In 2008, ICE arrested 424 criminal fugitives in San Diego County. In 2009, the number of arrests increased to 719.

"We take these people out of the community, it makes the community safer as a whole," said Baker.

Baker said he and his team will continue their efforts to keep San Diegans safe and keep dangerous criminals out.

This year, ICE anticipates spending more than $1 billion on programs that identify and remove illegal immigrants.