The death toll in the Philippines factory fire has risen to 72 as police begin to open a criminal investigation Thursday after a relative of several of the victims said the blaze trapped workers in the building's second floor where iron grills on windows prevented their escape.

Most of the bodies were retrieved from the two-story Kentex Manufacturing Corp. rubber slipper factory a day after the fire burned for over five hours in the outskirts of Manila.

As forensic investigators worked to identify the dead and reconcile their names with those listed as missing, questions were 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, told The Associated Press iron grills reinforced with fencing wire covered windows on the second floor that "could prevent even cats from escaping."

Candido said he was allowed to re-enter the building, where he saw charred remains "piled on top of each other" but could not say how many.

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.

Deputy Director General Leonardo Espina said police will file charges against "all those accountable and those at fault."

Valenzuela city fire marshal Me Jose Lagan said arson investigators will look into why people were unable to escape the burning building from the second floor where there was a "sufficient exit" that includes a wide stairway to the back of the building leading to the outside. They will also look into whether there were more people inside the building than allowed.

Iron grill bars on windows are common in offices, factories and homes in the country to keep thieves at bay. In workplaces or factories, they are also meant to stop employees from stealing equipment or products.

Valenzuela Mayor Rex Gatachalian said that a workers log bookc was lost in the fire and the foreman was among the dead, making it difficult to determine how many were inside the factory at the time.

The chief of the national police medical examiner's office, Emmanuel Aranas, said fingerprints could no longer be used to identify the burnt victims and forensic officers will have to rely on dental records, DNA and personal items to identify the bodies.
  
Gatchalian said the fire was apparently ignited by sparks from welding work 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.
  
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.

The Associated Press contributed to this report.