Minnesota prosecutors will not charge the billionaire chief executive officer of China's JD.com Inc, Richard Liu, after he was accused of rape by a University of Minnesota student during a recent U.S. visit, authorities said on Friday.

Hennepin County Attorney Michael Freeman said there were “profound evidentiary problems which would have made it highly unlikely that any criminal charge could be proven beyond a reasonable doubt.”

In a statement, Freeman said that after an investigation by Minneapolis police and a review by four senior sexual assault prosecutors, it was clear his office could not meet its burden of proof, and therefore could not bring charges.

“Because we do not want to re-victimize the young woman, we will not be going into detail,” Freeman said. 

The 45-year-old Liu, who grew JD.com from a humble electronics stall to an e-commerce giant with 2017 net revenues of 55.7 billion U.S. dollars and maintains tight control of the company, was released without charge about 17 hours after he was arrested on August 31. He quickly returned to China, where he has continued to run the company. His representatives have maintained his innocence after the woman from China studying at the University of Minnesota accused him of rape.

JD.com shares extended gains on Friday after news spread of the decision not to prosecute, and closed up 5.9 percent.

The case has attracted extreme interest in China.

The decision not to bring charges was a big relief for Liu, who could have faced as many as 30 years in prison under Minnesota law if convicted of first-degree criminal sexual misconduct.

On Friday, Freeman said the three months it took his office to review Liu's case was not unusual for a sexual assault investigation, especially one in which no one was in custody.

“It had nothing to do with Liu's status as a wealthy, foreign businessman,” Freeman said in his statement.

A lawyer for the student who accused Liu blasted Friday's decision, saying it showed why victims of sexual assault feared coming forward, and questioning why prosecutors waited to issue a release until late on the Friday before the Christmas holiday.

The investigators “never met this victim; they never spoke to this victim; they never sought to meet with her lawyers,” the attorney, Wil Florin, said in a statement. “Her story will be told. On her behalf we will not permit her dignity to be simply swept under the rug.”

The Hennepin County Attorney's Office did not immediately respond to a request for comment on Florin's statement.

An attorney for Liu said they welcomed the decision, and hoped that it would dispel “misinformation and speculation” that circulated widely since the billionaire's arrest.

“Mr. Liu was arrested based on a false claim, and after a thorough investigation, with which he fully cooperated, the declination of charges vindicates him,” Liu's attorney Jill Brisbois said in a statement.

Reuters previously reported details of what happened while Liu was in Minneapolis, including a description of the alleged attack and the events around it given by the now-22-year-old student.

Usually based in Beijing, Liu made the U.S. trip for a week-long residency program at the University of Minnesota's Carlson School of Management, which runs a doctor of business administration program with China's elite Tsinghua University.

The University of Minnesota said it had no comment on Friday's announcement by authorities.

The decision to not prosecute followed criticism of Minneapolis authorities, including Freeman's office, for what some see as a failure to pursue sexual assault cases adequately.

Liu, in a statement on Weibo, China's Twitter-like platform, this morning, said that he had cooperated fully with the investigation. "This proves I broke no law," he said. "I feel deep regret and remorse and I hope she [my wife] can accept my sincere apology. I will continue to try in every possible way to repair the impact on my family and to fulfill my responsibility as a husband."