MANILA—The death toll from a fire at a Philippine slipper factory rose to 72 on Thursday as police and firefighters searched the gutted two-story building for more bodies, authorities said.

The fire occurred at the Kentex Manufacturing Corp. factory in Valenzuela City, a suburb north of Manila, at noon Wednesday and lasted for several hours. Officials say the fire was apparently caused by an explosion from welding sparks, and an investigation is under way to determine whether any safety code violations contributed to the fire...