• Ningbo Lingjun sold $360 million of stocks withn a minute
  • The selling is deemed ‘abnormal’ behavior by exchanges

China’s two main stock exchanges froze the accounts of a major quantitative hedge fund for three days after the money manager dumped 2.57 billion yuan ($360 million) in shares within a minute Monday.

Ningbo Lingjun Investment Management Partnership executed the sell orders through multiple accounts starting from 9:30 a.m. as shares declined, “disrupting normal trading order,” the Shenzhen exchange said in a statement Tuesday. The Shanghai bourse imposed a similar freeze on Lingjun, which will be barred from trading stocks until Feb. 22.

The trading ban is the latest move by Chinese regulators to reverse a slump in stocks that’s now entering a fourth year. Quant funds are drawing particular scrutiny amid concerns they can amplify market volatility and fuel routs. The sector has dismissed these concerns.

Lingjun’s selling orders amounted to “abnormal trading behavior,” and the firm was warned multiple times for the same reason this year, according to the Shenzhen statement. The bourse will tighten supervision and maintain “zero tolerance” on any activities that harm investors’ legitimate rights, it said.

In separate statements by the Shenzhen and Shanghai bourses late Tuesday, the authorities said quant trading made by northbound investors via the mainland to Hong Kong stock connect will also be included in the reporting scope to the exchanges.

Lingjun, among the four-biggest quant funds in China with more than 10 billion yuan under management, didn’t respond to requests seeking comment.

China’s securities regulator made another move this week that underlines its resolve to shore up the nation’s $8.6 trillion stock market. The China Securities Regulatory Commission, led by new Chairman Wu Qing, will treat opinions, suggestions and criticism from all parties seriously and implement the “pragmatic and feasible” ones immediately, it said in a statement after holding a series of seminars with retail and institutional investors, listed companies and foreign institutions over the past two days.

China’s commodities exchanges ended commission rebates on some programmed trades this year, and regulators barred quants from cutting stock positions on certain products earlier this month in a bid to stem the market rout.

Written by: Bloomberg News — With assistance from John Liu, Dingmin Zhang, and Evelyn Yu @Bloomberg