Citadel account frozen amid probe

Citadel Securities LLC, the trading firm started by Ken Griffin, owns one of the 34 accounts frozen by Chinese bourses as authorities investigate whether algorithmic traders are disrupting the nation's stock market.

Bourses in Shanghai and Shenzhen have increased the number of suspended accounts from 24 announced on Friday, according to their websites.

The probe is focused on spoofing, a practice that involves placing and then canceling orders to move prices. Owners of the other frozen accounts include Infore Capital Management Co Ltd, a Shenzhen-based asset management company, and YRD Investment Co, a Beijing-based hedge fund.