NEW DELHI (AP) — Shares in India’s Adani Group plunged up to 20% on Friday and the company said it was considering legal action against U.S.-based short-selling firm Hindenburg Research for allegations of stock market manipulation and accounting fraud that have led investors to dump its stocks.

The heavy selling of Adani-linked shares, which wiped out billions of dollars worth of market value for India’s second-largest conglomerate, caused trading in some Adani companies to be suspended or temporarily halted on Friday.

So far, the impact has been mainly to Adani Group companies, though India’s Sensex index fell 1.5% on Friday and its Nifty index shed 1.6%. But analysts said there could be wider repercussions if the selling persists.

Gautam Adani and his family have built a vast fortune mining coal to fuel energy-hungry India’s fast-growing economy. Businesses in the conglomerate span industries including construction, data transmission, media, renewable energy, defense manufacturing and agriculture.

In recent years, Adani’s net worth has shot up nearly 2,000% to as much as $125 billion, according to Bloomberg’s Billionaire Index. He surpassed Amazon boss Jeff Bezos to briefly become the world’s second richest man in September after a surge in the value of his seven listed entities. After this week’s losses, Bloomberg’s index ranked him fourth richest in the world with a fortune worth $113 billion.

Adani shares were “trading at crazy evaluations,” said Shashank Aggarwal, an investment adviser representing Addwise Capital. “Definitely, the report has triggered a correction.”

Investors began unloading shares after Hindenburg Research issued a report that said it was betting against shares in companies in the Adani empire. Hindenburg said it judged the seven key Adani listed companies to have an “85% downside, purely on a fundamental basis owing to sky-high valuations.”

Brian Freitas, a New Zealand-based analyst with Periscope Analytics who has researched the Adani Group, said that for now he did not see a risk of wider financial contagion, “other than a change in sentiment where investors start questioning the accounts of each and every company.”

However, if Adani’s lenders demand more collateral and shares used for borrowing have to be sold to cover those demands, that would push prices still lower.

“In the event there is a sharp fall in the stocks then the financial institutions themselves could be at risk,” he said.

Aggarwal noted that members of the Adani family hold a large proportion of the group’s shares, leaving a relatively small number available for trading, which can increase price volatility.

If the issues raised in Hindenburg’s report are true, that might have a wider impact, he said. “Then the banking system gets affected. It is a highly leveraged company. They definitely have a lot of borrowings from the banks.”

After heavy selling on Wednesday, India’s markets were closed Thursday for a holiday. The bloodletting resumed in earnest on Friday, with shares in the flagship company Adani Enterprises falling 18.3%. Its shares fell 1.6% on Wednesday.

Some Adani companies suffered even bigger hits.

Shares in Adani Transmission plunged 20% on Friday after sinking 8.1% on Wednesday. Adani Green and Adani Total Gas also fell 20%. Adani Ports and Special Economic Zone Ltd. sank 15.2%.

Hindenburg said its report, “Adani Group: How the World’s 3rd Richest Man is Pulling the Largest Con in Corporate History,” followed a two-year investigation and “listed 88 questions it invited the company (Adani) to answer.” Most of the allegations involved concerns about the group’s debt levels, activities of its top executives, use of offshore shell companies and past investigations into fraud. It said Adani had not answered any of the questions.

Late Thursday, Jatin Jalundhwala, head of the Adani group’s legal department, said the group “was evaluating the relevant provisions under U.S. and Indian laws for remedial action against Hindenburg Research.”

“Clearly, the report and its unsubstantiated contents were designed to have a deleterious effect on the share values of Adani Group companies as Hindenburg Research by their own admission, is positioned to benefit from a slide in Adani shares,” Jalundhwala said.

Jalundhwala said the allegations were an attempt by Hindenburg to sabotage Adani’s share offering, which was undermined as the value of Adani Enterprises shares fell below the price range of the offering.

Hindenburg Research said in a rebuttal that it would welcome legal action by the Adani group.

“We fully stand by our report and believe any legal action taken against us would be meritless,” it said in a statement.

Freitas said he expected the weekend would give investors time to study the situation and Adani time to build a defense against Hindenburg’s criticisms.

“If you look at it more broadly, it’s not a great look for corporate India when a short-seller comes out with such a detailed report and the company is not able to rebut any of the arguments,” he said

“So it kind of raises doubts about corporate governance in India as a whole and how the regulator fits into the picture,” Freitas said.

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AP Business Writer Elaine Kurtenbach in Bangkok contributed.

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