China’s central bank is putting the spotlight back on bitcoin exchanges in the country.

This time, the People’s Bank of China (PBoC) has reportedly released the results of its inspection of the local bitcoin trading platforms. In it, investigators from the central bank described the “irregularities” they said they discovered in the operations of major bitcoin exchanges—BTC China, Huobi and OKCoin—which led to the recent “abnormal fluctuations” in the price of the popular digital currency.

According to Chinese-language news outlet JF Daily, the preliminary inspection by the PBoC’s Shanghai branch found BTC China offered loans, which is beyond the scope of its business as a bitcoin exchange.

In Beijing, central bank investigators also found alleged anomalies in the operations of OKCoin and Huobi. According to a separate report from Hexun, the three bitcoin exchanges offers a loan feature called margin trade, which the PBoC said not only violates the country’s rules but has also caused bitcoin’s recent volatility.