The blaze engulfed the Swastik Pesticide factory in Nai Mandi area, following which 10 fire tenders were pressed into service.
"It was a massive fire that took over five hours to be brought under control," Fire Officer Ajay Kumar told reporters in Muzaffarnagar, some 350 km from Lucknow.
"We had to call the fire tenders from three nearby districts. The workers trapped inside the factory were safely rescued with the assistance of police. However, two of our team members received minor injuries," he added.
According to officials, the fire was caused by an electric short-circuit.
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