Initial reports from the crime laboratory of the Philippine National Police (PNP) showed that Paulita Bonifacio, 50, died of massive head injuries.
Chief Superintendent Ernesto Belen, director of the crime laboratory, said Bonifacios companion, Marie Grace Ruiz, 37, a nurse, remain sedated in a hospital and could not be subjected to police interrogation.
"We are waiting for her to regain consciousness before asking her questions," Belen said.
Superintendent Ericson Velasquez, Mandaluyong City police chief, said there is no sign of forcible entry in the room of the victim at 724-A Sta. Ana St., Barangay Plainview.
Initial inventory also showed that the victims important belongings remain intact.
Velasquez said Bonifacio and Ruiz were both naked when found by police investigators inside the apartment.
Ruiz, who was in a state of shock, was said to be near the body of Bonifacio when found and was covered by a blanket.
Neighbors claimed that they heard Bonifacio and Ruiz arguing loudly at around about 9 p.m. on Sunday.
Velasquez said the Ruiz family had promised to cooperate fully in the investigation.