Security guards in the vicinity of the fire tried unsuccessfully to extinguish the flames before they called the local police fire brigade at 4:21 p.m. Authorities received two more calls, at 4:30 p.m. and 4:31 p.m. The Kader facility is just beyond the jurisdictional boundaries of Bangkok, but fire apparatus from Bangkok, as well as apparatus from Nakhon Pathom Province, responded.
As the workers and security guards tried in vain to extinguish the fire, the building began filling with smoke and other products of combustion. Survivors reported that the fire alarm never sounded in Building One, but many workers grew concerned when they saw smoke on the upper floors. Despite the smoke, security guards reportedly told some workers to stay at their stations because it was a small fire that would soon be under control.
The fire spread rapidly throughout Building One, and the upper floors soon became untenable. The blaze blocked the stairwell at the south end of the building, so most of the workers rushed to the north stairwell. This meant that approximately 1,100 people were trying to leave the third and fourth floors through a single stairwell.
The first fire apparatus arrived at 4:40 p.m., their response time having been extended because of the relatively remote location of the facility and the gridlock conditions typical of Bangkok traffic. Arriving fire-fighters found Building One heavily involved in flames and already beginning to collapse, with people jumping from the third and fourth floors.