India’s markets watchdog is probing Adani Group’s links to some investors in the group’s $2.5 billion share sale, two people said, as New Delhi grows concerned about US short-sellers’ attempts to control one of the country’s largest industrial conglomerates.

Two people with direct knowledge of the matter said the Securities and Exchange Board of India (Sebi) is looking into any possible breaches of India’s securities laws or any conflict of interest in the share sale process.

The regulator investigates the relationship between Adani and at least two Mauritian companies. Great International Tusker Fund and Ayushmat Ltd were involved as lead investors, two people said, speaking on condition of anonymity due to the confidential nature of the investigation.

Under India’s capital and disclosure requirements rules, any entity related to the company’s founders or founders’ group is not eligible to apply under the anchor investor category.

The Port Energy group, controlled by billionaire Gautam Adani, one of the world’s wealthiest men, has seen seven of its companies lose market value since Hindenburg Research’s January 24 report of more than $100 billion, the report accused it of improper use of offshore tax havens and stock manipulation. Adani has denied the allegations. Last week, the group’s flagship entity, Adani Enterprises, called off India’s largest-ever secondary share offering amid a sharp sell-off.

Sebi and Adani Group did not respond to requests for comment on the investigation. Great International Tusker Fund and Ayushmat Ltd. also did not respond to requests for comment.

Also under the Sebi scanner are Elara Capital and Monarch Networth Capital, two of the 10 investment banks managing the share offering, two people said, adding that Sebi had approached the two firms last week.