Gardai say it's too early to tell if a fire at Ballymount Industrial Estate was arson.
Dublin Fire Brigade is still trying to extinguish the blaze at the Oxigen plant, which broke out early on Saturday.
Three fire engines remain at the scene, and a new team of officers is being brought in to continue working.
Homes and businesses in the area have been told to keep windows are doors closed because of the toxic smoke.
