Firefighters were dispatched to Linden Bulk at 4200 Tremley Point Road around 9:15 a.m., Linden police said.
Workers from several surrounding buildings left the area due to the heavy smoke conditions before the fire was extinguished, just after 10 a.m., police said.
Union County Fire Mutual Aid units provided assistance on scene, including engines from the Elizabeth, Rahway, Roselle, Cranford, and Union Fire Departments.
Union County Hazmat personnel also responded, and will continue to conduct air monitoring in the area as a precaution.
Mayor Derek Armstead issued assured local residents there was no harm to the public.
"Many of you have heard the sirens, do not be alarmed... contrary to what has been posted by others no chemicals were ever compromised," he wrote.
"Therefore, there was no need to evacuate the neighborhood. No one was injured and everyone is safe."
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