The share price of Everbright Securities plummeted 8.54 percent to close at 9.21 yuan on Monday, while the benchmark Shanghai Composite Index remained basically unchanged from the last trading day, closing at 2,098.45 points.

Media reports have said a programmer at Everbright changed the stock brokerage's internal order-placing system it had developed to cover up a malfunction before the commission's investigative team arrived on site in an attempt to put all the blame on the outside supplier of the trading system.

The allegation was supported by a company source who was quoted as saying on condition of anonymity that the "fat finger" which caused the trading error was actually two software bugs, one in the trading system provided by the outside provider and the other in Everbright's own order taking system. The commission's investigation team was back in Shanghai last week after the initial three-day investigation starting from Aug 19 after they discovered the alleged tinkering.

Everbright spent about 100,000 yuan on the supplier's trading system. Other trading system providers charge about 1 million yuan. Everbright chose the supplier because the provider was willing to program the system to Everbright's specifications and requests, the source said.

He added the strategic investment department, from where the mistaken buy order was issued, is likely to be merged into other departments or the whole team will be dismantled.

The department mistakenly sent huge buy orders valued at 23.4 billion yuan on Aug 16. Of this, a total of 7.27 billion yuan was transacted. The big buy order was widely attributed to having lifted the index 5.96 percent in three minutes.

The commission banned the company from proprietary trading for three months and suspended approval for new Everbright services.

Everbright's net profit was around 1 billion yuan last year. Interim results show that it made a net profit of 811 million yuan in the first half of this year.