It appeared the three men and two women had been shot, but investigators were waiting for the Cook County medical examiner's office to confirm a cause of death, said Chief of Detectives Thomas Byrne. Autopsies were scheduled for Thursday, the medical examiner's office said.
"This is very serious," Byrne said at a news conference near the two-story house. "There's five victims. There's five families right now that are grieving over this."
All the victims were in their 20s, and they all knew each other, said Deputy Chief Eugene Williams. There were signs of forced entry into the house, which appeared to have been ransacked, Williams said.
A woman visiting the house found the bodies Wednesday afternoon, police spokeswoman Monique Bond said.
Police did not have offenders in custody but did not believe a killer was on the loose, Bond said. It was possible the victims knew the offender, she said.
"We don't think that the neighbors need to worry," she said. "We believe that it's been contained inside this residence."
Police declined to comment on whether the scene was a murder-suicide.
They cordoned off a section of the residential street as neighbors milled around, talked in groups and watched.
Bernard Scales, who said he is the grandfather of one of the victims, said the deceased were "good kids."
"They weren't gangbangers and they weren't into drug-dealing. I bet somebody over there thought they were into something, but they weren't," Scales told the Chicago Tribune.
The discovery comes on the heels of a spate of violence in Chicago. Nine people died in 36 shootings . The weekend shootings were scattered all over the city. Police said they included gang shootings, drive-by attacks, and even one case in which someone used an AK-47 to shoot up a plumbing supply store.
One man died and three others were wounded, including one of the alleged offenders, in shootings late Monday in a McDonald's restaurant parking lot on the South Side.
The recent violence followed a six-month period of deadly, reports CBS News correspondent Cynthia Bowers.
Since September, 24 students have been murdered. Last school year 34 students were killed, an average of one child getting murdered every eight days.