The rout in Indian stocks, triggered by the $16.5 billion fraud at state-run Punjab National Bank, has put the spotlight on billions of dollars that have flowed through Mauritius.

The Adani Group is one of the biggest investors in the African nation, with subsidiaries there that have been used to channel money out of India, according to people familiar with the matter.

The Adani companies have denied any wrongdoing. A spokesman for the group said its Mauritian entities are “fully compliant with all applicable laws and regulations.”

Mauritius is a key destination for Indian money because of its double taxation treaty with India. The treaty allows companies in Mauritius to avoid paying taxes on income earned outside the island nation.

The Adani Group has been one of the biggest beneficiaries of that arrangement. Its subsidiaries in Mauritius have reported more than $2.5 billion in income over the past decade, according to a review of company filings.

That income has helped finance a string of big investments by the Adani Group in India, including a port in the western state of Gujarat and a $2 billion coal mine in the eastern state of Odisha.