The call came in around 2 p.m. Thursday for an unresponsive 2-year-old girl on the 6300 block of Marsden Street.
Police say the child appeared to have trauma marks on her face and body.
The girl was transported to St. Christopher's Hospital for Children where she later died.
"Very disturbing case of child abuse. The child sustained horrific injuries," said Philadelphia Police Homicide Captain Jason Smith.
Police are not releasing the child's name at this time.
Neighbor Marisela Rivera said, "It's so sad. It hurts me because what could that child have done so wrong to deserve such abuse."
Investigators say the child was staying with her godmother at the Marsden Street home because her mother's house on the 3300 block of Hartville Street in West Kensington had been without heat since November.
Who is responsible for the abuse is still being investigated, officials say.
Police say both women, whose names have not been released, are being questioned by homicide detectives.
Police are still working to determine what led to the child's death.
No charges have been filed at this time.