China's market regulator has begun an antitrust probe into Didi Chuxing ahead of the ride-hailing startup's IPO in the US, Reuters reported. The SAMR is investigating whether Didi used any competitive practices that squeezed out smaller rivals unfairly, it added. Didi's IPO is expected to be the biggest Chinese IPO in New York since Alibaba's $25 billion float in 2014.