(CNN) Now that police believe a Chicago woman killed a pregnant teen, cut the unborn baby from her womb and pretended the infant was hers, the hospital that received the baby is under investigation.

Police say Clarisa Figueroa, 46, strangled 19-year-old Marlen Ochoa-Lopez in Chicago on April 23 and then called 911 on the same day to say she'd just delivered the baby.

Figueroa and the baby were taken to Advocate Christ Medical Center in nearby Oak Lawn.

The Illinois Department of Public Health is investigating Advocate Christ Medical Center, spokeswoman Melaney Arnold confirmed. She declined to provide additional information, citing "an ongoing investigation."

Illinois law requires that physicians and other hospital personnel who suspect child neglect or abuse report their suspicions

The Department of Child and Family Services was not contacted by the hospital until May 9, one day after police found Ochoa-Lopez's car, CNN affiliate WGN has reported

"The sheriff's office will consult with DCFS on whether the circumstances of this case required DCFS be notified," the Cook County Sheriff's Office said in a statement obtained by WGN

Marlen Ochoa-Lopez, 19

"If DCFS says they should have been notified, the sheriff's office will conduct an investigation into what happened."

An Advocate Christ Medical Center spokesman told CNN on Monday that he could not comment on the case.

"Our top priority is to provide the safest and highest quality care for the patients and communities we serve. Out of respect for patient privacy and in compliance with federal and state regulations, we are unable to provide comment. We continue to cooperate with local authorities," medical center spokesman Adam Mesirow said.

Cook County prosecutors said there were no signs that Figueroa had given birth. Ochoa-Lopez's relatives have said they don't understand why the hospital wouldn't have reported suspicions earlier.

Ochoa-Lopez's husband reported her missing on April 24, police say.

Police say they only began to suspect Figueroa was connected to Ochoa-Lopez's disappearance on May 7, after a friend of Ochoa-Lopez told detectives that Figueroa and the teen had been in contact with each other on Facebook

After a DNA test showed the baby wasn't Figueroa's, investigators searched Figueroa's house May 14 and found the teen's remains in a trash can in a back yard, police said.

The baby has been continuously hospitalized , in intensive care.

Figueroa and her daughter, Desiree Figueroa, who police say helped in the strangulation, were charged with first-degree murder and battery of a child last week.

Clarisa Figueroa, 46, Desiree Figueroa, 24, and Piotr Bobak, 40

Clarisa Figueroa's boyfriend, Piotr Bobak, 40, was charged with concealing the death of a person and concealing a homicidal death.

All three are being held without bond.

Frank Avila, a lawyer for the family of Ochoa-Lopez, told reporters Monday that he also wants to know whether the hospital followed protocols.

"If I see somebody coming in with a baby ... why does the mother look like she's in good health that has no blood, normal clothes. That doesn't make logical sense to me," Avila said.