CHICAGO (CBS) — A 35-year-old man has been accused of forcing 12 girls into prostitution, and addicting them to heroin.

DaJuan Brown has been charged with 10 counts of involuntary servitude and one count of aggravated trafficking in persons. He was ordered held on $1 million bond on Wednesday.

CBS 2’s Roseanne Tellez reports on why law enforcement is on high alert for this type of crime right now.

“This arrest reminds us that this type of activity is taking place here in Cook County,” Cook County State’s Attorney Anita Alvarez said.

LISTEN: WBBM Newsradio’s Lisa Fielding reports

Alvarez said demand for sex services often spikes around the time of major sporting events, conventions or other major events.

Sex traffickers know it, so they try to take advantage of the increased demand by moving victims of forced prostitution around, much like drug traffickers move narcotics around, depending on where it’s being bought.

“When people are coming here, (from) out of town, and tourists are coming in, we see an increase in the demand, or the seeking of this type of activity,” Alvarez said.

She said she wants sex traffickers and potential customers to know that the type of crime Brown is accused of won’t be tolerated.

Authorities said, over the last five years, Brown kept young women padlocked in an Austin neighborhood apartment building, letting them out only to sell sex.

Brown would take the money they got from their johns, and if the prostitutes didn’t do as they were told, they were beaten.

“There were beatings involved, heroin — getting the women addicted to the heroin. So, it really was some horrific things that happened in this case,” Alvarez said.

Police said Brown gave the women heroin several times a day to keep them addicted, and would often reward them for meeting their quotas by giving them more heroin.

Neighbors said they were shocked to find out what was going on in the building where Brown kept his victims, but they said they did wonder what was going on in the building before Brown was arrested.

One woman said she suspected something was going on, “because he was an Afro-American man, and he had this parade of other ethnic group women, young women, with him.”

The victims – some of them still teenagers – have been getting help from social service groups.

If convicted of the charges, Brown would face up to 30 years in prison.