New York (CNN Business) Minnesota prosecutors will not file sexual assault charges against Richard Liu, the billionaire CEO of Chinese e-commerce giant JD.com.

Liu, 45, had been arrested in Minnesota in late August on suspicion of rape. He was let go without being charged and without having to pay bail. He returned to China soon after his release.

Hennepin County Attorney Mike Freeman said in a statement Friday that the months-long investigation by police and prosecutors found "profound evidentiary problems" that would have made it hard to build a criminal case.

"As is the case in many sexual assault incidents, it was a complicated situation," Freeman said. "It is also similar to other sexual assault cases with the suspect maintaining the sex was consensual."

Freeman said that as prosecutors reviewed surveillance video, text messages, police body camera video and witness statements, they realized they could not bring charges. The investigation was triggered when a college student at the University of Minnesota called police on August 31 and said Liu had raped her at her off-campus apartment.

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