The income tax department will put to the test a bilateral tax treaty with Mauritius to glean information from the tax haven on investors in Indian Premier League teams as part of a wide-ranging probe into the shadowy flow of money into the T20 cricket tournament.

A detailed and full-fledged investigation will now be carried out on all IPL franchisees and the people behind them, a tax department official told ET.

The department will soon write to the Mauritius government asking it to shed light on investors after preliminary information and data on shareholding of some IPL franchises point to flow of funds from complex multi-layered structures in the country, he said.

The cash-rich tournament as well its high-profile commissioner Lalit Modi have long been under the tax departments scanner over allegations that more than one IPL team have foreign stakeholders. But it was only after Mr Modis public smackdown with junior foreign minister Shashi Tharoor that officials have delved deeper into IPLs murky world.

A team of tax officials visited the IPL headquarters in south Mumbai last Thursday and quizzed Mr Modi late into the night. Documents collected from the IPL office and a few franchisees point to a shareholding web and use of accounts in tax havens to make payments, another official told ET.

The taxman has already put the screws on IPL team owners, notably Rajasthan Royals Jaipur IPL Pvt Ltd. Tax authorities have conveyed their reservation to the Foreign Investment Promotion Board, the key government body on foreign investments, on Jaipur IPLs proposal of seeking post-facto approval on raising FDI after issue of shares.

The company was asked to justify direct payments from a Mauritius-based entity even before creation. The department also suspects other tax havens such as Bahamas, the Maldives, Macau and Cayman Islands, among others, but gathering information will not be easy as the country is still in talks for similar agreements with these countries. Tax officials say there are also indications of some shareholders fronting for others in some franchises.

Mr Modi himself has family links with at least one IPL team. Suresh Chellaram, a Nigeria-based businessman who is learnt to own a 44% stake in Rajasthan Royals, is Mr Modis brother-in-law. Similarly, Kolkata Knight Riders, owned by actors Shah Rukh Khan, Juhi Chawla and husband Jai Mehta, has close links with Bollywood producer Karim Morani. He is also referred as a stakeholder but details of the stake have been kept under wraps. Email queries to Kings XI Punjab as well as Kolkata Knight Riders remained unanswered.

Deccan Chargers, owned by media group Deccan Chronicle Holdings of Hyderabad, is the only team to declare its ownership structure. Three teams Delhi Daredevils, Mumbai Indians and Chennai Super Kings have a sole owner.