TRENTON, N.J. – Two adults and three juveniles have been charged with gang-raping a 7-year-old girl who was sold by her 15-year-old stepsister during a party at a crime-ridden apartment building, police said Saturday.

Details on the arrests were announced at a Saturday night news conference at police headquarters in Trenton, the state’s capital city.

The arrested people include a 20-year-old man who already had been charged Friday with having sex with the 15-year-old. The other four are a 19-year-old Trenton man and boys ages 13, 14 and 17. Each was charged with aggravated sexual assault and child endangerment.

Police said further arrests may be made in the case, which shocked residents of the Rowan Towers apartment building.

Authorities say the 7-year-old girl was offered for sale by her stepsister on March 28. They say the stepsister went to a party with some men at Rowan Towers and the younger girl tagged along because she worried about her stepsister’s safety.

Police say the 15-year-old sold sex to men, then took money to let them touch the younger girl. They say touching turned to forcible sex as at least seven men raped the 7-year-old.

Before Saturday’s arrest announcement, the 15-year-old had been charged with promoting prostitution, aggravated sexual assault and other crimes; police have not released her name, and she remained in juvenile detention Saturday night.

Mayor Doug Palmer said he met with the victim’s relatives at his office on Thursday to offer help and make sure they were able to move out of the neighborhood over safety concerns.

“We made sure they got out of the area,” he said Saturday before the news conference.

He pledged to spare no expense “to make sure that everyone responsible is brought to justice.”

“We’re still asking the community to let us know if they have any more information on this heinous crime,” he said.

Rowan Towers is surrounded by blocks of abandoned, boarded-up homes.