Founded in 1998, JD.com is an e-commerce juggernaut in China and the main competitor to industry leader Alibaba. The alleged assault would be a felony, authorities said, declining to provide further detail.
A Minneapolis police department spokesperson said over the weekend the investigation was "active" but Liu hadn't been charged.
The Nasdaq-listed JD.com has made headway in its battle with e-commerce giant Alibaba by operating its own logistics network and providing Chinese customers with same-day or next-day delivery for many of their purchases.
JD said it planned to make a selection of items available for sale in places like Europe and the U.S. through Google Shopping, which allows shoppers to search for products and compare prices on different e-commerce sites.
FILE PHOTO - JD.com founder Richard Liu attends a Reuters interview in Hong Kong, China June 9, 2017. Liu will continue his business trip as planned, the company said.
The firm, also known as "Jingdong", got its name from a combination of part of Liu's Chinese first name, Qiangdong, and that of his girlfriend at the time, Xiaojing.More news: A Peek Inside A Teen Prince Harry's Eton College Dorm Room
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The website of Hennepin county in Minnesota said Liu was released from custody on Saturday.
Following the Chinese media accounts, JD.com said on its official microblog that the reports were untrue.
Liu was apparently in Minneapolis because he is enrolled as a student at the University of Minnesota's Carlson School of Management in its Doctor of Business Administration China program.
The New York Times reported Liu has returned to China where he has become the talk of the nation. Among its other investors is Chinese internet gaming and social media giant Tencent Holdings, the developer of the WeChat messenger app and a major rival of Alibaba, and USA retailer Walmart Inc.
His wife, Zhang Zetian, some 19 years younger, is a businesswomen and internet celebrity.
Liu's arrest comes as the billionaire is still trying to distance himself from a sexual assault that occurred at a party he hosted in his luxury Sydney penthouse in 2015.
Longwei Xu, a property developer, was later found guilty of seven counts.