Other probes are ongoing and have cast an aura of caution over the industry, said a senior NTPC executive.

WSJ: Graft Worries Slow India Coal Imports

More than half of the country's electricity comes from coal-powered plants and NTPC relies on coal for 80% of its generation capacity.

WSJ: Graft Worries Slow India Coal Imports

But as NTPC's recent experience shows, such imports could face delays due to an increased focus in India on reducing corruption in the coal industry.

WSJ: Graft Worries Slow India Coal Imports

Last year, Mr. Choudhury, the company's chairman, said fear of probes into alleged wrongdoing was slowing decision-making at NTPC over operational issues, including whether to buy overseas coal blocks to reduce supply deficits.

WSJ: Graft Worries Slow India Coal Imports

Only small amounts of the tender so far have been procured, meaning NTPC was only able to import 9 million tons of coal in the year to end-March, short of its 16-million-ton target.

WSJ: Graft Worries Slow India Coal Imports