Indian billionaire Gautam Adani, one of Asia’s richest men, may be facing his biggest challenge yet with an indictment by U.S. prosecutors for alleged fraud and bribery. But it’s unclear just how the case will affect his businesses and own future — as well as the Indian economy and government.

Shares of Adani Group companies lost about $28 billion in market value in morning trade on Thursday after U.S. prosecutors charged the billionaire chairman of the Indian conglomerate in an alleged bribery and fraud scheme.

A US indictment threatens Indian tycoon Gautam Adani’s efforts to redefine himself as a clean-power champion and secure overseas financing for projects vital to the nation’s energy transition.