China Longyuan Power Group Corp, the nation's biggest wind-power producer, may raise about $500 million by selling shares in Hong Kong, three people with knowledge of the matter said.

Longyuan, which said in May that it would offer up to 1.36 billion shares in Hong Kong, is planning to offer about 813 million shares, two of the people said, who asked not to be identified because the information is private. The company's advisers have been gauging investor interest in the offering this month, the people said.

The final timing of the sale hasn't been decided, and will depend on Longyuan's market price. At its closing price of HK$4.85 apiece on Monday, a sale of 813 million shares would raise about HK$3.9 billion ($503 million). The stock slipped 0.8 percent to HK$4.81 apiece as of 3:26 pm in Hong Kong trading on Tuesday.