A judge in Mexico has ordered two federal detectives and two ex-detectives to stand trial on charges of kidnaping for extortion for allegedly holding 15 South American women briefly to demand a bribe for not reporting them to immigration authorities.

Mexico City police detained the detectives last week after receiving a plea for help from one of the women.

The detectives claimed they were investigating the 15 women from Venezuela, Argentina and Paraguay in a human-trafficking case. Such cases often involve prostitution in Mexico.

But officials allege the four men actually held the women briefly and demanded one million pesos (about $58,000) for not deporting them.

Local media reported the women were apparently working at a nightclub and may have held only tourist visas.