MINNEAPOLIS (AP) — Twenty-one people have been indicted in what authorities are calling a sophisticated sex-trafficking ring that brought hundreds of women from Thailand to America and forced them to work as prostitutes.

Authorities say the members of the ring also laundered millions of dollars in earnings.

The case announced Thursday builds upon an indictment unsealed in October.

The indictment unsealed Thursday says the sex-trafficking ring started in 2009. Women were brought from Bangkok, Thailand, to several U.S. cities, including Los Angeles, Chicago, Las Vegas, Phoenix, Minneapolis, Washington, Houston and Dallas.

The women were lured with promises of a better life, but were forced to work as "modern day sex slaves" until they paid back bondage debts.