Carlyle Group and TPG Capital are among buyout firms in talks with Reliance Communications about purchasing a stake in its mobile-phone towers unit, three people with knowledge of the matter said.

Reliance Communications has also received interest from potential investors including Blackstone Group LP , the world''s biggest private-equity firm, and London-based Apax Partners LLP, said one of the people, who declined to be identified because the discussions are private.

The Mumbai-based company received "formal indicative offers from several interested parties" for its Reliance Infratel unit, it said in a statement to the Bombay Stock Exchange on May 31, without naming any bidders. The mobile-phone operator's board approved taking the sale process to the next stage of due diligence, according to the release.

The company in June 2010 it was in "advanced talks" to sell about 50,000 telephone towers.

Gaurav Wahi, a spokesman for Reliance Communications in Mumbai, didn't immediately respond to a call seeking comment. Blackstone said in an e-mailed response that it doesn't comment on industry speculation. Dorothy Lee, a spokeswoman for Carlyle in Hong Kong, and Ben Harding, a spokesman for Apax in London, declined to comment. Tim Payne, an external spokesman for TPG, couldn't immediately be reached for comment.

The company may sell a majority stake in the unit, the people said. Reliance Communications in August scrapped a deal to sell the business to GTL Infrastructure Ltd. Reliance's debt exceeded cash and equivalents by Rs 32,000 crore ($7.16 billion) as of March-end from Rs 19,900 crore a year earlier., according to the mobile operator.