A new report revealing the potential size of China's housing market bubbles, coupled with price control measures announced by the national regulatory body, sent share prices for key property developers tumbling Thursday.

The report, published Wednesday by the Chinese Academy of Social Sciences (CASS), set alarm bells ringing as it revealed the worrying truth about the size of the housing bubbles in major cities.

In a measure to control runaway prices, the China Banking Regulatory Commission said Wednesday that it was cracking down on real estate risk, by obliging real estate investment trusts to become responsible for gauging the likely compliance risks of businesses entering the real estate market.

A-lister Poly Real Estate Group saw its share price drop 4.5 percent to 12.13 yuan ($1.80).

Its fate was mirrored by that of China Vanke, the country's largest developer, with its stocks falling by 3.8 percent to 8.17 yuan ($1.21).

Bloomberg reported that the Shanghai Composite Index's gauge of property developers indicated a sector-wide drop by 1.8 percent, its largest fall since November 26.

A bubble describes the portion of the housing price average exceeding the base price, which is measured in turn by 11 sub-indexes such as the average per capita income of residents, as well as public infrastructure and facilities.

The report measured the average housing bubble among 35 large and middle cities at 29.5 percent, with Beijing and Shanghai among 11 cities where bubbles floated between 30 to 50 percent of the market price.

The worst culprit was identified as Fuzhou, in eastern Fujian Province, where the gap between market value and real prices reached a staggering 70.3 percent.

"The housing price has kept rising for years. This has inflated investor expectations for high returns, which have brought money flooding into the market, thus contributing to enlarging the bubbles," Zou Linhua, co-author of the Chinese Academy of Social Sciences report.