The United States has widened its investigation of India's Adani Group to focus on the conduct of its founder, Gautam Adani, and whether the company may have engaged in bribery, Bloomberg News reported on Friday.

Prosecutors are digging into whether an Adani entity or people linked to the company, including Gautam Adani, were involved in paying officials in India for favourable treatment on an energy project, the report said, citing people with direct knowledge of the matter.

The US Attorney's office for the Eastern District of New York and the Justice Department's fraud unit in Washington are handling the investigation and are also looking at Indian renewable energy company Azure Power Global, the report added.

"We are not aware of any investigation against our chairman," Adani Group told Bloomberg News. Adani Group, Azure Power and the DOJ did not immediately respond to Reuters' requests for comments. The Attorney's Office for the Eastern District of New York could not be immediately reached.

Adani Group's stocks and bonds saw a massive selloff early last year after US short-seller Hindenburg Research issued a report that alleged improper governance practices, stock manipulation and the use of tax havens by the group. The Indian company has denied these allegations.