The fire department was called to Hulbert Lumber Co. at 37500 Cedar Blvd. shortly after 9 a.m. on a report of an employee feeling unwell, department spokeswoman Aisha Knowles said.
The hazardous materials team was called in around 9:25 a.m. after firefighters learned the employee, a 27-year-old man, had become dizzy and passed out while attempting to clean up a spill of an unknown substance, Knowles said.
The chemical was spilled after a forklift driver accidentally hit two 5-gallon containers in a storage area, knocking the lid off one of them and spilling some of the substance it contained, Knowles said.
Knowles had initially said the drum was punctured by the forklift.
The affected employee was taken to a hospital, but is believed to be fine this afternoon, Knowles said.
About a dozen employees at the business were evacuated from the site while the hazardous materials team made entry, but were allowed to return around 1 p.m., according to Knowles.
The hazardous materials team has isolated the open container inside another larger container and is collecting samples to send to a lab to identify the substance, Knowles said.
No other businesses or homes in the area were evacuated or affected by the incident.
Newark police were also on the scene providing traffic control and backup.