It took six hours Wednesday for firefighters to get the upper hand on the blaze at the National Surtrex Corp on McLean Boulevard.
Two firefighters suffered minor injuries.
Officials also had to close a section of Route 20. Ramps to nearby Interstate 80 were also closed.
Firefighters had difficulty accessing the building and ran fire lines over nearby freight train tracks, affecting service on New Jersey Transit.
The company is a large distributor of medical and safety disposable apparel.
The cause of the fire is under investigation.
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