The value of futures traded across China's three biggest commodity exchanges has shrunk 42 percent since investors spent 1.7 trillion yuan last Thursday on everything from steel bars to eggs. The amount that changed hands was on a par with the entire U.S. equities market on the same day.

Markets in the world's biggest consumer of raw materials have been gripped by a trading frenzy that's drawn comparisons with the credit-driven stock market rally last year that preceded a $5 trillion rout. Exchanges have responded by raising margins and transaction fees to curb speculation while the securities regulator is said to have prepared measures to limit price fluctuations.