Authorities said testing revealed Michele Kalina, 44, was the mother of all five babies and that at least four of them were the result of an extramarital affair with a boyfriend, WFMZ-TV, Allentown, Pa., reported.
Kalina allegedly hid the bodies in a closet in her Reading apartment where she lived with her husband and teenage daughter, the TV station said.
The daughter discovered the remains and notified authorities. Investigators determined the daughter had unknowingly discarded one set of remains, which were later recovered from a landfill.
"These remains were all badly decomposed skeletal remains," Berks County District Attorney John Adams said. "Four of the human remains were term birth, post-natal death due to non-natural, violent cause and means consistent with asphyxia, poisoning or neglect."
Investigators said they believe Kalina acted alone, and that she lied to her husband and boyfriend to keep her pregnancies a secret.
"She'd indicated to her boyfriend that she had had ovarian cysts," Adams said, "and that is why she began to show."
Adams said she may be charged for each infant's death later, depending on trial strategy.
Kalina has been jailed since her arrest in August.