Christensen, 28, who has a master's degree in physics from the University of Illinois, was arrested on charges of kidnapping Zhang, 26, on June 30.

On July 5, he was ordered held without bail by US Magistrate Judge Eric Long in federal court in Urbana, Illinois.

Acting US Attorney Patrick Hansen and FBI Special Agent in Charge Sean Cox announced the return of the indictment.

A preliminary hearing scheduled on July 14 was cancelled, according to a statement released by the US Attorney's Office in the Central District of Illinois on Wednesday.

A date for Christensen's arraignment will be scheduled by the US Clerk of the Court in Urbana.