SANTA ANA, California (AP):

Juan Martinez was looking forward to returning to his construction job after finishing a month-long sentence for violating probation on drug charges.

But when he was finally released from the Orange County jail, he was met by immigration agents - not his mother. The 23-year-old illegal immigrant was set to be deported with US$68 in his pocket and few prospects.

"I just probably won't come back," he said about being sent to Tijuana, Mexico. "If I do, I'll keep coming back to prison and I don't want that."

Martinez is among tens of thousands of illegal immigrants being identified at jails and prisons across the country.

Considered strategic checkpoints in the search for illegal immigrants, the lock-ups are being monitored by an increasing number of federal agents who screen foreign-born arrestees and deport those without proper documentation.

Federal authorities are also enlisting the help of local authorities to check out immigrants who are arrested.

"There is a growing recognition that criminal aliens prey on the community at large," said Virginia Kice, a spokeswoman for U.S. Immigration and Customs Enforcement (ICE). "ICE is doing internal restructuring to enhance coverage of jails."

Past efforts to nab illegal immigrants in jails were haphazard and overtaxed, with federal authorities checking inmate rosters at some facilities once a week or less. The situation allowed some of the worst immigration violators to avoid detection and get back on the streets after serving time.

Conservative immigration groups are pleased with the new strategy but worry that the emphasis on jail checks is a political ploy that threatens to divert much-needed personnel and other resources from stopping illegal border-crossers.

"This is a way to do it that everybody is for but has no real effect on the overall immigration flow," said Mark Krikorian, executive director of Center for Immigration Studies, a conservative think tank. "It shuts up the critics."