SHANGHAI, June 1 (Reuters) - China's major stock indexes opened mixed on Wednesday after posting their biggest gain in three months on Tuesday, on expectations U.S. market index provider MSCI could add mainland stocks to its emerging market benchmark for the first time.
The CSI300 index rose 0.1 percent to 3,172.40 points at 0132 GMT, while the Shanghai Composite Index lost 0.1 percent to 2,915.14 points.
The China Financial Futures Exchange said on Wednesday morning that sell orders from a hedging client triggered technical selling that caused a flash crash in one futures contract on Tuesday, a blip in an otherwise positive day for China's long dormant futures markets, which rallied along with major indexes.
China CSI300 stock index futures for June rose 0.4 percent, to 3,154.8, 17.60 points below the current value of the underlying index.
The Hang Seng index in Hong Kong was down 0.1 percent, at 20,797.15 points. (Reporting by Pete Sweeney; Editing by Jacqueline Wong)