It's not clear if the cold weather was a factor. The baby was bundled up in a snow suit. The children were discovered in an apartment in the 3700-block of West 13th Street.
Police were interviewing the mother of the children on Wednesday night.
Police and fire officials swarmed the apartment in the 3700-block of West 13th street Wednesday afternoon after a neighbor called 911 to report neglected kids in their shared building.
Police could be seen removing an infant car seat from the apartment from which the neighbor said a 6-year-old girl had emerged, looking for food. The neighbor went to the unit and found a 7-month-old baby and a 2-year-old girl -- and no parents or caregivers.
The children were taken to Mt. Sinai Hospital, where the infant was pronounced dead. Fire officials originally said the baby had frozen to death, but later reported she was found in a car seat, with an apparently 100 degree temperature, wrapped in winter clothes and blankets. The other children remain at the hospital.
On Wednesday night, several of the building's occupants and passersby declined to comment on the situation. Managers of the property dropped by, but left without getting into the apartment.
The medical examiner has not yet released the identity of the dead infant.