Fire broke out in a blade manufacturing factory in Thane in the Wagle estate locality on Monday, fire officials said.
The incident took place in the early hours, around 0230 am, destroying a major portion of the plant, they said.
More than two dozen fire tenders have been pressed into service to douse the flames, fire brigade said.
Firemen are still fighting the blaze that engulfed the Panama company, they said.
The cause of the fire is unknown and fire officers are on the spot to supervise the operations.