An allegation of police brutality has prompted a broader Montgomery County Police investigation into the role that two officers might have played in helping federal agents detain a Montgomery Village man without charging him with a crime.

In the wake of the Sept. 22 detention, county police took the rare step of asking for a special visa that would prevent the man's deportation while they investigate the incident.

County police also are looking into how the 26-year-old man — who authorities believe is in the United States illegally — ended up in the custody of U.S. Immigration and Customs Enforcement.

Although ICE can detain anyone it believes might be in the country illegally, an 8-month-old county policy requires Montgomery officers to refer people to ICE only when they are arrested and charged with certain serious crimes.

A day after the man was shackled by federal agents last month in Montgomery Village, Police Chief J. Thomas Manger authorized a memo to all officers reminding them of the county's practice not to refer anyone to ICE solely on the basis of immigration status or "perceived gang affiliation."

The case has sparked worry among Latino advocates that the man was referred to federal authorities in retaliation for an earlier complaint he filed against a county officer.

"How can we as an organization continue to tell young people that we are proud of them to believe in this when I myself right now can't believe in this policy?" said Candace Kattar, director of Identity Inc., a Gaithersburg-based nonprofit that works with youths at risk of joining gangs, and helped the man file his complaint. "I can't, right now, believe that this policy will be respected by officers."

The police internal investigation stems from a July 21 incident in Montgomery Village in which a county officer accused the man, a driver for a moving company, of being a member of the violent Mara Salvatrucha gang, or MS-13, based on his tattoos, according to the complaint.

The man, who is not being named because he is a witness in an ongoing police case, had told Identity that he was a gang member in his native El Salvador, but has not been involved in gang activity since coming to the United States in 2006.

Submitted to police Aug. 18, the complaint claims the man was in Centerway Local Park with his two children and their mother at about 8 p.m. July 21, after the park closed.

While checking on the family, Officer David Marshall used the man's Maryland driver's license to see if he had any outstanding arrest warrants.

After the routine check, the man was released but his license was not returned, according to Identity. An internal police investigation determined that police lost the license, Kattar said.

After the man attempted to track down what happened to his license, he claims an officer retaliated. The morning of Sept. 22, the man was allegedly assaulted by a different officer, said Melissa Crow, a Baltimore attorney who represents the man.

According to affidavits compiled by Identity — including statements by witnesses and family members — the man was struck in the head by an unknown officer who "hit him so hard that it flipped the guy over," Kattar said.

The man said that ICE agents, who were accompanying county police, put him in shackles and took him to its field office in Baltimore, Crow said.

Hours after the man was detained, Latino advocates brought the case to police attention and met with Manger the following day.

Police are investigating the conduct of Marshall and Officer Scott Zimmerman, said Capt. Paul Starks, a police spokesman.

A criminal probe concluded two weeks ago without charges.

"There was not enough evidence or facts to support criminal charges," Starks said.

Marshall and Zimmerman are the two gang investigators in the department's 6th District, which covers parts of middle and upper Montgomery County. Both officers said that they had no comment.

Starks would not comment directly on the allegation of brutality, how the license was lost or when the investigation could conclude.

The police chief said he is taking the matter seriously.

"[A]t some point I will be very forthcoming about what occurred, what we did right, what we did wrong and address the issue," Manger said.

"We've done a lot of investigation," the chief said. "What we have not done — you've got to talk to everybody and get your background stuff done and then you talk to the officers involved. We're at the point where we're getting ready to talk to the officers involved."

County Executive Isiah Leggett (D) has been briefed about the case and has since conferred with members of his Latin American Advisory Group.