Federal authorities in Arizona are expected to crack down soon on businesses that knowingly hire undocumented workers, joining a nationwide effort to bust employers most responsible for the job magnet that attracts illegal immigrants to the United States.

Russell "Pete" Ahr, a spokesman for Immigration and Customs Enforcement in Phoenix, said the agency's worksite enforcement unit has been beefed up to pursue felony charges against those who willfully use unauthorized labor.

"It is active now," Ahr said of the unit. "It is conducting investigations. There are going to be visible results in the foreseeable future. ... We're not fining (companies) anymore. We're going after criminal indictments against the owners."

During raids, some illegal immigrants are likely to be arrested for deportation. But, Ahr emphasized, ICE agents will not conduct random sweeps to round up undocumented workers. They will use tips and intelligence to identify business operators who purposely violate the law.

Ahr declined to say what industries or types of businesses may be targeted.

The crackdown comes at a time when illegal immigration is a hot political issue, with grass-roots lobbying, election campaigns and congressional feuding over reform.