Mainland stocks tumbled Thursday as investors braced for a possible interest rate rise and a flood of new share sales, the South China Morning Post reported. The benchmark Shanghai Composite Index fell 4.8% to close at 1,655.77 points and the Shenzhen Composite Index slid 5.4% to 422.44 points. Speculation of another interest rate rise and further macroeconomic tightening measures came after unofficial figures were published claiming the economy grew 10.9% in the second quarter despite government attempts to reduce growth. The drop comes as 10 companies were scheduled for IPO approval reviews with the securities regulator in the past two weeks. "In the next few days, we could see a further correction but it is very unlikely the market will drop below 1,560 points," Zhang Qi, an analyst at Haitong Securities, told the newspaper.