Wilberto Kwan Tiu said that all 38 victims trapped inside the mall died of suffocation due to the release of toxic chemicals such as hydrogen cyanide (which was produced by the carpets and plastics) and carbon monoxide by the fire. Kwan Tiu said that the BFP will investigate the cause of the fire. Davao City fire marshal Honeyfritz Alagano said that the mall had insufficient ventilation and that all the emergency exits in the mall were operational, except for the one in the fourth floor where the SSI office was located. Davao City Mayor Sara Duterte said that a third party investigator would represent the families of the victims, which was supported by the city government. She added that a multiagency task force led by the Department of the Interior and Local Government called the Interagency Anti-Arson Task Force (IAATF) would investigate the incident. On December 28, 2017, Duterte declared that the NCCC mall was "fire safety compliant". Alagano confirmed that the mall contained the necessary fire safety requirements, such as a fire alarm system, a fire sprinkler system, and emergency exits. However, she could not confirm whether these systems were inoperative at the time of the incident, as reported by some survivors. NCCC's spokesperson Thea Padua said that the mall was inspected by fire officials annually in order to renew its business permit. Padua added that safety drills were conducted in the mall quarterly, the last one occurring on July 14, 2017. On December 29, 2017, the IAATF deduced that the mall's emergency exits, which were inside the building, failed to meet certain requirements. IAATF investigator Jerry Candido said that the law requires interior emergency exits to be enclosed in order to prevent the entry of smoke. However, the IAATF discovered that the mall's interior emergency exits contained openings which allowed smoke to enter. The IAATF also discovered that the fire alarm system at the SSI office was defective, compatible to allegations made by some survivors which the NCCC management had denied. In addition, the fire alarm system at the SSI office was not connected to the NCCC's system. The IAATF later discovered that the mall's automatic fire suppression system did not function in the third and fourth floors as the valves of the fire sprinkler system were closed. The IAATF cited these loopholes as the reason for the failure of the victims to escape the building. On January