Four people were charged this week with running an underage sex trafficking ring in Brooklyn Park.

At least three girls were sold for sex through online advertising or through a dating application between August 2017 and March 2018, according to a criminal complaint filed Monday. One of the girls was a 15-year-old runaway.

The sex took place in cars in the parking lot of a Brooklyn Park apartment complex. The head of the ring, Michaella Collins, 26, of Milwaukee, made the girls pay for rent through robbery, prostitution and drug sales, the complaint said. They all lived in Collins’ apartment.

Collins, Lanesha Morgan-Franklin, Brendian Daniels and Raphael Powell were charged with felony counts of promoting prostitution with victims under 18. A warrant was issued for Collins’ arrest.

The Hennepin County Attorney’s Office said it would seek an aggravated sentence because the victims were particularly vulnerable as runaways and because crimes were committed for extended period of time.