Massive clouds of black smoke were seen rising from a fire at an incineration plant along Tuas Avenue 10 on Friday evening.
According to the Singapore Civil Defence Force's Facebook post, fire fighters arrived within eight minutes after receiving an alert at 5.17pm.
They said that there were three casualties with burn injuries who were sent to the hospital, adding that the fire, which involved "flammable chemicals", was approximately the size of two football fields.
A total of 60 SCDF personnel were involved in the operation. They used 12 cooling jets, including two platform monitors "for aerial fire fighting".
A spokesperson said that they took about 90 minutes to put out the fire.
According to eyewitness Lim Gee Sin, a project manager who works in a factory about 200m away, the fire appears to have started from the Fuji Chemical building. It has since spread to Fabristeel, and his factory has been evacuated, he added.
He said he also spotted two super ladder fire engines in the vicinity.