Baring Private Equity (Asia) is in advanced talks with Blackstone Group LP
The sources declined to give a monetary value or specify the amount of the stake being sold, but said the deal would end up valuing the unlisted company at about $400-450 million.
Blackstone had paid $65 million for a 57% stake in CMS Info Systems from then owner CMS Computers in 2009.
Carlyle Group
They declined to be named as the negotiations are still private.
"Baring is clearly the front runner. We aim to close the deal before year-end," said one of the sources.
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Blackstone has mandated Rothschild (India) to run a formal auction process for CMS Info Systems, the sources added.
Blackstone, Carlyle, Temasek and Rothschild all declined to comment, while Baring Asia did not respond to an e-mail seeking comments.
CMS provides ATM management, cash delivery and pick-ups and cash-in-transit services among others.