The proceeds from the sale, amounting to about $20 million, will primarily be used to support the business in India, the source said.
The company later said in a stock exchange filing that promoter group firm Samanvaya Holdings Pvt Ltd had sold the stake in an open market block deal. It did not disclose the identity of the buyers.
The shares had changed hands in a block deal on the National Stock Exchange earlier on Thursday at Rs 27.15 a share.
Suzlon shares, which plunged to an all-time low of Rs 25.35 earlier, closed 12 per cent lower at Rs 25.65 in a weak Mumbai market.