BHP said its initial findings of the Nov. 5 incident showed the nearly 3-km (1.9 miles) long train came to a halt after a braking system control cable became disconnected.
Eskom, which supplies more than 90 percent of the nation's power, has warned of potential power outages amid low coal inventories after a major supplier cut supplies and sought insolvency protection.
The Tamil Nadu state disconnected the smelter's power supply in May following anti-pollution protests that turned violent and culminated in the police opening fire, killing 13 protesters.
Following the news, NMDC shares fell as much as 7.4 percent to 99.20 rupees, their lowest since July 25, marking their biggest single-day fall since Aug. 9.
While the project known as S11D isn’t scheduled to hit its 90-million-ton capacity until 2020, China’s appetite for the mine’s low-cost, high-grade ore continues to grow.
China, the leading holder of international deep sea exploration licences, increases its lead in the race for alternative sources of battery minerals by taking samples from cobalt-bearing mountains deep in the Pacific.
Cavalcanti joins Samarco as it attempts to renegotiate billions of dollars in debt with creditors and restart operations after a tailing dam burst in 2015, killing 19 people.