
"These are very dangerous situations here, not only dangerous situations for our community, but also extremely dangerous for our officers who have to go out and track these guys and arrest these folks," Anderson said.
Click here to watch a Phoenix police sergeant on the job.
In some cases, dozens of people at a time have been kidnapped. They are often illegal aliens whose captors then demand ransom from the victims' relatives in Mexico.
ABC News followed Sergeant Phil Roberts in Phoenix on a day when his unit was working on three on-going kidnapping cases and trying to find a victim in peril.
"Our victim's probably being brutalized, he's probably being beaten up and tortured and God knows what else is taking place," Roberts told ABC News. "And we don't know whether he's a legal or illegal. We look at it as if he's a human being. He's being tortured out there, and we've got to do everything we can to try and rescue that individual."
Watch Brian Ross' full report tonight on Nightline at 11:30 p.m. ET.