Reading police say 44-year-old Michelle Kalina was being held Tuesday on $5 million bail.
Investigators said they responded to a call on July 29 about remains inside a hallway closet of her first-floor apartment, and discovered the bones of baby, estimated to be at 20 weeks gestation, along with a one-month-old baby inside a blue cooler.
A Berks County forensic anthropologist estimated the ages of the remains but the genders weren't immediately determined.
Forensic testing results are not back yet, so there is no word on how the babies died.
Investigators said, during the course of an interview on Monday, Kalina acknowledged her ownership and control of the closet in which the remains were located. She was arrested a short time later.
Kalina was committed to Berks County Prison in lieu of bail.
Her husband and 17-year-old daughter, who live with Kalina, are not facing charges at this time.
District Attorney John Adams said additional charges could be filed. The investigation is ongoing.
A news conference on this case is expected within the next week.