WASHINGTON — US immigration authorities have more than quadrupled the number of jobsite inspections for illegal workers in two years, a government report said Wednesday.

In fiscal year 2010, officials with Immigration and Customs Enforcement (ICE) initiated a "record" 2,746 worksite enforcement investigations, said the report submitted to Congress by the agency's deputy head Kumar Kibble.

That's more than double the 503 inspections in 2008.

Fines for 237 violations reached almost seven million dollars, compared to the 18 violations and 675,209 dollars in penalties in 2008.

Kibble told lawmakers ICE was focused on identifying "criminal illegal aliens who pose a threat to the public."

The Department of Homeland Security (DHS), which oversees ICE, has "fundamentally reformed immigration enforcement," he said.

Republicans, who now dominate the House of Representatives, have criticized President Barack Obama's approach to immigration as weak.

Kibble noted DHS "has engaged in record enforcement, removing more aliens in both 2009 and 2010 than in any point in the history of our country, including more than 195,000 criminal aliens last year."

Advocacy groups representing migrants have meanwhile criticized what they call heavy-handed raids in Hispanic communities along the US-Mexico border.

"ICE is now taking custody of more aliens encountered at the border and is increasing the consequences for illegal entry and reentry," Kibble said.

"Aliens who illegally enter in Arizona, for instance, are no longer given the opportunity to return voluntarily and instead are given orders of removal and are repatriated through other states."

The southwestern state of Arizona has seen more illegal immigrants than anywhere else along the border, and has been the scene of bitter political standoffs on immigration issues between the tough approach of the state government and the federal government's softer stance.