Video footage posted on the internet showed black smoke plumes rising from the fire at the site of the blast on Saturday.
Local media reported firefighters were working to contain the blazing inferno at the Kayan Petrochemical plant owned by Saudi Arabia Basic Industries Corporation (SABIC).
Sounds of gunfire were also reported, Press TV reported.
Jubail is reportedly the host of the largest industrial area in the Middle East.
The city is also home to the largest petrochemical company in the region.
The industrial area is heavily guarded by police against possible militant attacks.