The Maoists attacked a facility of NMDC Ltd in Chhattisgarh and set 200 metres of conveyor belt on fire early Wednesday, police said.
The incident took place around 1 a.m. at NMDC Deposit-5 at Bacheli in the state's Dantewada district, police said.
After hearing the news, NMDC officials, trade union leaders, Central Industrial Security Force troopers and fire brigade personnel rushed to the spot.
The fire could be controlled after three hours.
NMDC officials at Bacheli said the incident was one of the biggest attacks in recent years on NMDC facilities in Chhattisgarh.
The attack has resulted in heavy loss and created panic in the entire Bacheli and Kirandul residential pockets.