It was not human error, but design flaws in a trade unit of China Everbright Securities that triggered the anomalous trades on Friday, according to the China Securities Regulatory Commission (CSRC) on Sunday.

The Everbright proprietary "strategy trading system" has flaws in aspects like program call and limit control and the flaws were triggered sequentially, resulting in huge orders at market prices, said a CSRC spokesperson.

The total declaration for buying totalled 23.4 billion yuan (3.8 billion US dollars) and the actual transactions topped 7.27 billion yuan, the spokesperson said.

The erroneous trade caused a swift rise in domestic A-share stocks in minutes at the end of Friday morning trade. The benchmark Shanghai Composite Index spiked 5.96 percent within three minutes on Friday.