The blast occurred late on 23 November and was reportedly caused by a gas compressor exploding.
No one has been reported killed or injured in the incident. Emergency officials at the scene have said the fire has been "localized."
The ethylene-polyethylene plant, which is part of the state-run AzerChemistry company, is located 35 kilometers north of the Azerbaijani capital Baku.
(compiled from local and international news reports)