Hortencio Firfan-Mancilla, 44, is charged with knowingly transporting women across state lines to engage in prostitution.

Eduardo Garcia Lopez, 33, is charged with aiding and abetting the effort.

Both men also face charges of harboring illegal immigrants and conspiracy.

The defendants, who are being held without bail, will be arraigned Tuesday.

Teresita Soledad-Saldevia, allegedly an illegal immigrant and prostitute from Uruguay, was being held as a material witness. No federal charges have been brought against her. Another alleged prostitute and illegal immigrant, Colombian Doris Usma, has not been located.

Both men admitted they were running a prostitution operation, court documents say. Garcia-Lopez, whom Soledad-Saldevia referred to as "boss," would drive the women to meet with customers. Firfan-Mancilla would hold on to the money and watch the women whenever the "boss" was away.

Firfan-Mancilla also transported the two women from Columbus, Ohio, to Shelbyville last month, federal prosecutors allege.

The prostitutes and Firfan-Mancilla apparently worked for Garcia-Lopez, court records say.

Shelbyville Police Sgt. Richard Babiarz discovered the house of prostitution on July 12, after responding to a disturbance in an apartment building.

Officials say they believe Garcia-Lopez, who used the alias Juan Lopez, also ran a brothel out of the LaFontenay Apartments in Louisville. According to an affidavit signed by federal immigration agent Michael T. Moreland, two bedrooms in the sparsely furnished apartment contained only mattresses. Sex toys and "excessive condoms" were also present.

Last month, federal law enforcement officials shut down brothels in Los Angeles, San Francisco, and Hudson County, N.J., where illegal immigrants were being forced or coerced to engage in prostitution.

But the Kentucky case appears to be different.

"Fortunately, it's probably not ... a human trafficking case in which individuals have been forced against their will," said U.S. Attorney Gregory F. Van Tatenhove. "But it's troubling nonetheless to have a case where there are individuals, here illegally, who have been brought into prostitution."

Federal officials say it's rare for them to uncover brothels run by illegal immigrants in Kentucky. "I do not recall another recent case like this one," Van Tatenhove said.

If convicted of transporting the women, the men face up to 10 years in prison and a $250,000 fine. The conspiracy charge carries an identical penalty. The penalty for harboring the women is up to five years in prison and a $250,000 fine.

All four immigrants are likely to be deported.