Jessica Marie Mauthe, 39, was arrested after her former landlord called police to the home she had lived in outside Ford City, about 40 miles northeast of Pittsburgh.
The landlord, Brent Flanigan, told WTAE-TV that he had law enforcement evict Mauthe for nonpayment on Aug. 14.
After he began cleaning the home, he came across a trash bag in a closet that had a foul odor and something wrapped in towels that was decomposing, according to the arrest affidavit issued Thursday.
Investigators searched the home and found the bodies of three other infants in the attic in tote bags, wrapped in towels and inside plastic bags, police said.
"Shocked. No one believed it. It's just evil," neighbor Carmen Felix told WTAE-TV. "How can you plop babies in the toilet?
Mauthe was charged with criminal homicide, involuntary manslaughter and multiple counts of abuse of a corpse. She is being held in the Armstrong County Jail without bail.