The U.S. Justice Department is investigating the city of Alpharetta's denial of a request last year by the Islamic Center of North Georgia to expand its facility on Rucker Road.

A Justice Department spokesman said Friday that the agency is investigating the case under the Religious Land Use and Institutionalized Persons Act, passed in 2000. The act requires local governments to show that zoning decisions against religious groups are the least restrictive way to accomplish a compelling government interest. The law also prohibits governments from making decisions favoring one religion over another.

"I think it certainly indicates the Justice Department thinks the city of Alpharetta may not have acted entirely according to the law," said Andrea Jones, an attorney for the Islamic Center. "But it's an investigation. They haven't said that."

Officials with the city had no comment Friday, and the city attorney was not available.

The Alpharetta City Council voted 6-0 last May to reject plans by the center to tear down its 2,500-square-foot worship house and construct two buildings: a 1,900-square-foot multipurpose facility and a 12,000-square-foot, two-story main building.

A crowd of 150 squeezed into council chambers to hear several hours of arguments, including residents of surrounding subdivisions who said the project was too big for the 4-acre lot and would make traffic worse on Rucker Road. But most residents and the council said they were concerned that the worship center was backing out of previous agreements made before Alpharetta annexed the property in 2005.