Milton Galarza-Rojas died on July 29, shortly after medics responded to a 911 call of a baby not breathing.
The medical examiner's office recently received the results of toxicology tests and ruled the baby died from an overdose of heroin and cocaine.
Arrest warrants have been issued for the child's aunt 27-year-old Viameri Santana-Berrious and her 34-year-old boyfriend Oscar Rivera.
A police spokeswoman said the couple may have fled to Puerto Rico.
Anyone with information about their whereabouts should contact the Philadelphia Police Homicide Unit.