The fire broke out in the Interstate Waste Services transfer station garbage bays on Railroad Avenue shortly after 4 a.m. Thursday, Detective Lt. Vincent Aiello said.
Two employees tried to extinguish the blaze with a fire hose before firefighters took over, he said.
One of the employees was brought to Hackensack Meridian Health's Pascack Valley Medical Center in Westwood with smoke inhalation, Aiello said.
Demarest firefighters joined their Closter colleagues at the former site of Miele Sanitation.
The Closer and Harrington Park volunteer ambulance companies also responded, along with borough police, Aiello said. The state Department of Environmental Protection was notified, he said.
Click here to follow Daily Voice North Hunterdon and receive free news updates.