The U.S. Securities and Exchange Commission is investigating Didi after its tarnished initial public offering, adding further pressure on the Chinese ride-hailing giant.
Didi said in its annual report, published Monday, that it was contacted by the SEC after the company went public. The SEC "made inquiries in relation to the offering," Didi said.
"We are cooperating with the investigation, subject to strict compliance with applicable PRC laws and regulations. We cannot predict the timing, outcome or consequences of such an investigation."
Didi did not give further details about the probe. The company did not respond to a request for comment when contacted by CNBC.
Didi went public in the United States last June, raising more than $4 billion.
Shortly after, Chinese regulators opened up a cybersecurity probe into the company. Didi's app was also removed from app stores in China.
In December, Didi said it would make plans to delist from the New York Stock Exchange and prepare for a listing in Hong Kong.
Didi shares fell more than 5% in premarket trade on Wednesday. The company's stock is down around 85% since its IPO.