Emergency government measures designed to curb a free fall in the Chinese stock market last week have apparently succeeded in stabilising the market. Now regulators have turned their attention to the root causes of the boom-bust cycle.

Late on Sunday the China Securities Regulatory Commission warned brokerages not to open their trading systems to so-called fund-matching companies that distribute grey-market margin loans to investors, with few safeguards. Such lending occurs outside the regulatory framework that governs margin finance by brokerages.

“Leverage by itself isn’t necessarily threatening,” says Liu Yuhui, a researcher at the Institute of Finance and Banking at the Chinese Academy of Social Sciences, a think-tank advising the government. “The problem is that it’s not transparent. Regulators can’t see what’s going on. That’s very dangerous.”