Last year, state banks made a record $1.4 trillion in loans, nearly twice as much as the year before. Analysts say they believe much of that money was diverted into the property market through off-balance-sheet maneuvers, leading to the record land bids and soaring property prices. That belief is adding to concerns that some of China’s biggest state-owned banks may be sitting on enormous unreported debt.

Beijing is now struggling to rein in credit without slowing the nation’s roaring economy. And regulators are trying to stop state banks from using clever maneuvers to secretly lend money to overly aggressive state-owned developers.

Beijing also wants to restrain state companies that have little or no expertise in real estate. Last March, the State Assets Supervision and Administration Commission  one of the national government’s most powerful bodies  ordered 78 state-owned companies to shed their real estate divisions.

But analysts say the government will have difficulty stopping hundreds of state-owned companies and their various subsidiaries from participating in what has become one of the country’s hottest industries. Experts say that more than 90 of the 125 state-owned companies directly under Beijing’s control still have property divisions. And local and provincial governments control many additional developers.

The national government is grappling with a complex set of incentives that drive state-run companies to speculate in the property market with the aid of local governments.

Rosealea Yao, an analyst at Dragonomics, a research consultant in Beijing, says a growing number of municipalities have formed local investment vehicles that borrow heavily from state-owned banks to pay to relocate residents and build infrastructure around big plots of land they intend to sell at auction. (In China, local governments cannot directly borrow from banks or issue bonds for real estate development.)

Those off-balance-sheet debts are essentially bets on rising land prices, she says, which could become big liabilities if land prices were to decline sharply or the auction market were to dry up.