The share price for IT services group Mahindra Satyam has tumbled by 11% in the wake of new charges against the company's former chairman B Ramalinga Raju and nine others.
India's Central Bureau of Investigation (CBI) said the alleged accounting fraud at the former Satyam Computer Services was significantly larger than previously stated by Ramalinga Raju.
The CBI said the total fraud is now believed to be $2.6bn up from the original figure of $1.5bn, according to the Financial Times.
Ramalinga Raju was arrested for cheating and forgery in January after confessing to the board that he had manipulated the company's accounts over several years.
Indian authorities seized control of the company, which was acquired by Tech Mahindra in April and renamed Mahindra Satyam.
The CBI said Ramalinga Raju and nine others had used various methods of fraud to raise money including loans by forging board resolutions and dividends received by inflating company profits.