The blaze swept through the slipper and shoe factory in Valenzuela City on Wednesday, sending huge clouds of thick black smoke billowing into the sky.
Investigators were still pulling bodies from the charred ruins a day later.
Many of the dead were recovered from the second floor of the building, authorities said, suggesting people had become trapped there.
It wasn't clear Thursday whether fire officials expected to find any more bodies in the burnt-out shell of the factory, which was owned by the Kentex Manufacturing Corp.
One of the factory owners said the log book containing the list of workers on duty was lost in the blaze, making it difficult to determine exactly how many people were inside the factory at the time, according to authorities.
Sparks from welding may have started blaze
The city government said initial investigations indicated the fire was caused by sparks from welding work on the factory's gate that set alight chemicals in nearby containers. The chemical compounds were for the production of rubber slippers.
The flames spread in seconds, witnesses said.
"We tried to put the fire out by pouring water and using the fire extinguisher but it was difficult already," Steve Chua, a worker in the factory, told police, according to CNN Philippines
The choking black smoke from the highly combustible materials hampered firefighters' efforts to extinguish the blaze and find survivors.
The fire, which started before noon Wednesday, was eventually put out by the evening. Police officials searched for clues in the wreckage Thursday for the ongoing investigation.
Five people pulled alive from the burning factory on Wednesday were taken to local hospitals. Authorities said late Wednesday that the total number of survivors was still unclear.
Bodies burned beyond recognition
Weeping relatives had waited anxiously for news of loved ones. But the hopes of many withered as the death toll rose through the day Thursday.
Body bags were lined up outside the blackened remains of the factory and then taken to a local government building
The bodies have been burned beyond recognition and will need to be identified by forensic experts using descriptions of teeth, height and other physical characteristics, officials said.
Valenzuela City Mayor Rex Gatchalian told victims' family members that authorities would provide them with support, including help with burials, food and health care. Authorities said they had set up an assistance center for families.
Flags at the city hall flew at half-mast Thursday.
The city is part of the densely populated metropolitan region around the Philippine capital, Manila.