UPDATE: Family Members Says Workers Were Trapped As Massive Philippine Factory Fire Kills 58

Members of Scene of the Crime Operatives of the Philippine National Police line up body bags containing the remains of victims Thursday, May 14, 2015, a day after a fire gutted Kentex rubber slipper factory in Valenzuela city, a northern suburb of Manila, Philippines. (AP Photo/Bullit Marquez)

Police recovered 58 bodies and about a dozen more people are still missing Thursday from a Philippine factory fire that an angry relative said had trapped workers on the second floor of the building where iron grills on windows prevented their escape.

The search for bodies resumed after it was suspended late Wednesday because of the heat and worries about the instability of the two-story building, a rubber slipper factory in the outskirts of the Philippine capital, Manila.

Mayor Rex Gatchalian of Valenzuela city, where the Kentex Manufacturing Corp. factory burned for several hours Wednesday, said 13 people are still unaccounted for.

Questions are being raised if the factory followed fire and building safety standards.

Dionesio Candido, whose daughter, granddaughter, sister-in-law and niece were among the missing, said iron grills reinforced with fencing wire covered windows on the second floor that "could prevent even cats from escaping."

He said he was allowed by authorities to enter the gutted building, where he saw charred remains "piled on top of each other."

Gatchalian said the fire was apparently ignited by sparks from welding work being done at the factory's main entrance door, triggering an explosion of the chemicals used to make the slippers.

Workers fled to the second floor where they were trapped, he said. He was unsure if there were any fire escapes there.

Firemen work to put the fire under control at a still-smoldering Kentex rubber slipper factory in Valenzuela city, a northern suburb of Manila, Philippines, Wednesday, May 13, 2015.

District Fire Marshal Wilberto Rico Neil Kwan Tiu said that the building had other exits but apparently the workers were overwhelmed by the thick black smoke from the burning rubber and chemicals, which are highly flammable and caused the blaze to spread quickly.

Local media reports quoted relatives as saying their kin sent text messages saying they were on the second floor, but contact was lost shortly after.