DENVER - The federal government is rapidly expanding a program to identify illegal immigrants using fingerprints from arrests, drawing opposition from local authorities and advocates who argue the initiative amounts to an excessive dragnet.

The program has received less attention than Arizona's new immigration law, but it may end up having a bigger impact because of its potential to round up and deport so many immigrants nationwide.

The San Francisco sheriff wanted nothing to do with the program, and the City Council in Washington, D.C., blocked use of the fingerprint plan in the nation's capital. Colorado is the latest to debate the program, called Secure Communities, and immigrant groups have begun to speak up, telling the governor in a letter last week that the initiative will make crime victims reluctant to cooperate with police "due to fear of being drawn into the immigration regime."

Under the program, the fingerprints of everyone who is booked into jail for any crime are run against FBI criminal history records and Department of Homeland Security immigration records to determine who is in the country illegally and whether they've been arrested previously. Most jurisdictions are not included in the program, but Immigration and Customs Enforcement has been expanding the initiative.

Since 2007, 467 jurisdictions in 26 states have joined. ICE has said it plans to have it in every jail in the country by 2013. Secure Communities is currently being phased into the places where the government sees as having the greatest need for it based on population estimates of illegal immigrants and crime statistics.

Since everyone arrested would be screened, the program could easily deport more people than Arizona's new law, said Sunita Patel, an attorney who filed a lawsuit in New York against the federal government on behalf of a group worried about the program. Patel said that because illegal immigrants could be referred to ICE at the point of arrest, even before a conviction, the program can create an incentive for profiling and create a pipeline to deport more people.

"It has the potential to revolutionize immigration enforcement," said Patel.

Patel filed the lawsuit on behalf of the National Day Laborer Organizing Network, which is concerned the program could soon come to New York. The lawsuit seeks, among other things, statistical information about who has been deported as a result of the program and what they were arrested for.

Supporters of the program argue it is helping identify dangerous criminals that would otherwise go undetected. Since Oct. 27, 2008 through the end of May, almost 2.6 million people have been screened with Secure Communities. Of those, almost 35,000 were identified as illegal immigrants previously arrested or convicted for the most serious crimes, including murder and rape, ICE said Thursday. More than 205,000 who were identified as illegal immigrants had arrest records for less serious crimes.

In Ohio, Butler County Sheriff Rick Jones praised the program, which was implemented in his jurisdiction earlier this month.

"It's really a heaven-sent for us," Jones said. He said the program helps solve the problem police often have of not knowing whether someone they arrested has a criminal history and is in the country illegally.

"I don't want them in my community," Jones said. "I've got enough homegrown criminals here."

Carl Rusnok, an ICE spokesman, said Secure Communities is a way for law enforcement to identify illegal immigrants after their arrest at no additional cost to local jurisdictions. Jones agreed.

"We arrest these people anyway," he said. "All it does is help us deport people who shouldn't be here."

Rusnok said ICE created the program after Congress directed the agency to improve the way it identifies and deports illegal immigrants with criminal backgrounds. ICE has gotten $550 million for the program since 2008, Rusnok said.

Rusnok said the only place he knows of that has requested not to be a part of Secure Communities is San Francisco, which began the program June 8. Eileen Hirst, the chief of staff for San Francisco Sheriff Michael Hennessey, said it happened "without our input or approval."

Hirst said the sheriff thought Secure Communities cast too wide a net and worried that it would sweep up U.S. citizens and minor offenders, such as people who commit traffic infractions but miss their court hearings. Hirst also said the program goes against San Francisco's sanctuary city policy that calls for authorities to only report foreign-born suspects booked for felonies.

"Now, we're reporting every single individual who comes into our custody and gets fingerprinted," Hirst said.

California Attorney General Jerry Brown denied Hennessey's request to opt out. Brown said that prior to Secure Communities, illegal immigrants with criminal histories were often released before their status was discovered.

This month, Washington, D.C., police decided not to pursue the program because the City Council introduced a bill that would prohibit authorities from sharing arrest data with ICE out of concern for immigrants' civil rights. Matthew Bromeland, special assistant to the police chief, said police wanted the program and were talking with ICE about how address concerns from immigrant advocates before the bill forced them to halt negotiations.

Colorado officials became interested in the program after an illegal immigrant from Guatemala with a long criminal record was accused of causing a car crash at a suburban Denver ice-cream shop, killing two women in a truck and a 3-year-old inside the store. Authorities say the illegal immigrant, Francis M. Hernandez, stayed off ICE's radar because he conned police with 12 aliases and two different dates of birth.

A task-force assembled after the crash recommended Secure Communities as a solution.

Evan Dreyer, a spokesman for Colorado Gov. Bill Ritter, said Ritter recognizes that other states have had issues with the program and he wants to take time to consider the concerns raised by immigrant rights groups before deciding "how or if to move forward."

The Colorado Immigrant Rights Coalition said in its letter to the governor that the Secure Communities is "inherently flawed and should not be implemented." CIRC said one of its main concerns is that in cases of domestic violence, where both parties may be taken into custody while authorities investigate a case, victims may feel reluctant to report a crime out of fear that their illegal status will be discovered.

ICE maintains that only suspects arrested for crimes - and not the people reporting them - will be screened for their legal status.

Online:

Secure Communities: http://www.ice.gov/secure-communities/