Trading in the business empire of Asia's richest man Gautam Adani was halted Friday following a 15 percent plunge in its share price, days after a US investment firm claimed it had committed "brazen" corporate fraud.
Flagship Adani Enterprises tumbled to 508.45 rupees ($6.23) in Mumbai in the afternoon, triggering an automatic 105-minute trading halt, while subsidiary Adani Total Gas also halted after it tanked 20 percent.
Adani, 60, was the world's third-richest person on Wednesday, but on Friday fell to seventh place on Forbes' billionaires tracker after losing $19 billion when trading resumed in India following a Republic Day holiday.
Adani's sprawling interests range from Australian coal mines to India's biggest ports and the combined market cap of its seven listed companies exceeded $218 billion at the start of the week.
The conglomerate said Thursday it was the victim of a "maliciously mischievous" reputational attack by Hindenburg just as it was preparing for a major fundraising round.
Legal chief Jatin Jalundhwala said in a statement that Hindenburg's short-sell position in the firm, announced in the report's release, was proof the company had a vested interest in driving down Adani stocks.
Adani was exploring its punitive action against the research advisory in US and Indian courts, he added.
"If Adani is serious, it should also file suit in the US," the firm said in a statement. "We have a long list of documents we would demand in a legal discovery process."
Shares in Adani business units have soared as much as 2,000 percent in the past three years, adding more than $100 billion to its founder's net worth and vaulting him up the ranks of the world's richest people.
Adani -- who now has an estimated fortune of around $120 billion -- is considered a close supporter of Prime Minister Narendra Modi.
Hindenburg's report accused Adani Group of engaging in a "brazen stock manipulation and accounting fraud scheme over the course of decades".
It claimed Adani's elder brother Vinod managed "a vast labyrinth of offshore shell entities" in tax havens including Mauritius, Cyprus and several Caribbean islands.
The report said a pattern of "government leniency towards the group" stretching back decades had left investors, journalists, citizens and politicians unwilling to challenge the group's conduct "for fear of reprisal".
Its allegations come as an ambitious $2.5 billion follow-on public offer -- India's biggest-ever -- opened for bids on Friday, aimed at bolstering the business empire's balance sheet.
The Mumbai stock exchange's NIFTY benchmark was down nearly two percent after the halt.