MEXICO CITY (Reuters) - U.S. authorities have charged seven men with sex trafficking after a crackdown against a gang operating across the U.S.-Mexico border for at least 16 years, the U.S. Justice Department said on Tuesday.

Six suspected members of a sex trafficking organization known as STO were arrested last week and a seventh man remains at large, said U.S. Attorney General Lorreta Lynch and Manhattan U.S. Attorney Preet Bharara.

From at least 2000, STO members used romantic promises, physical and sexual violence, threats, lies and coercion to make women and girls work in prostitution in both Mexico and the United States, the Justice Department said in a statement.

Bharara accused the defendants of raping, beating, torturing, and enslaving their victims. Fourteen victims of the STO were identified in the 21-count indictment unsealed in the U.S. District Court for the Southern District of New York.

Four of the men charged were apprehended by Mexican authorities, and two were arrested in the United States.

(Reporting by Natalie Schachar; Editing by Dave Graham and LIsa Shumaker)