WASHINGTON (CNN) -- Twenty-six Bosnian Serb refugees are in custody after a series of raids around the United States targeting people who served in Bosnian Serb military units that attacked Muslims. Officials say three others remain at large.

Sixteen of the 29 face criminal charges for concealing their military service when they applied for refugee status in the United States.

A court document says one of them, Nedjo Ikonic, 40, of Greenfield, Wisconsin, "was a commander of a police company that cooperated with and was subordinated to the Army of the Serbian Republic during the July 1995 massacre in Srebrenica."

Units of the Bosnian Serb army are accused of torturing and executing at least 7,000 Muslims in Srebrenica, a United Nations-designated "safe area."

The 16 were indicted on charges of immigration fraud or lying about their Bosnian Serb military background on their immigration applications. They face five to 10 years in prison if convicted.

Thirteen others detained only on administrative immigration violations face deportation.

The arrests by Immigration and Customs Service agents occurred over several days in Florida, Wisconsin, Colorado, Michigan, North Carolina and Ohio, according to Justice Department officials familiar with the operations.

"These cases demonstrate our resolve to identify and prosecute those who enter this country under false pretenses, especially those who hide their military past," said Deputy Attorney General Paul McNulty.

The U.S. investigation followed a U.N. war crimes tribunal in The Hague, Netherlands.

One official said some Bosnian Serbs fled the United States earlier this month after they were initially interviewed by immigration agents.

The largest number of arrests occurred Monday in Tampa, Florida, where eight suspects were apprehended. Several of them were arraigned in U.S. District Court there and pleaded not guilty.