(Reuters) - Family members of a Chinese scholar presumed kidnapped in Illinois asked President Donald Trump on Tuesday to provide additional resources to help find her.

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Yingying Zhang, a 26-year-old visiting scholar to the University of Illinois from southeastern China, disappeared on June 9. Police believe Zhang is dead, although no body has been found.

Brendt Christensen, a former master’s student at the university, has been charged with abducting Zhang. Christensen, 28, pleaded not guilty to the kidnapping last month and is scheduled to stand trial in September.

Yingying Zhang’s father, Ronggao Zhang, cited the president’s own role as a father in a letter sent to Trump earlier this month and read by Zhang’s boyfriend, Xiaolin Hou, at a news conference on Tuesday.

“As a loving father to your own children, you can understand what we are going through,” the letter said. “We fervently request that you direct all available federal law enforcement and investigatory resources be used to find our daughter as soon as possible.”

A White House representative could not immediately be reached for comment.

Hou also told reporters at the news conference in Champaign, Illinois, that he and the family would not return to China until Zhang is found.

An online fundraising platform has collected more than $137,000 to support the family’s stay in the United States.

The case has been watched closely by Chinese media, China government officials and Chinese students in the United States.

Zhang, who had been studying photosynthesis and crop productivity, was last seen when a security camera recorded her getting into a black car that authorities linked to Christensen, according to court documents.

Christensen was placed under surveillance by federal agents who heard him talking about how he kidnapped Zhang, court records said. He could receive a life sentence if convicted.

Christensen’s attorney, Anthony Bruno, said in a phone interview on Tuesday that the defense received more than 1,000 pages of police reports related to the case earlier this month, and expects to gain access to video evidence soon.

Bruno said the defense plans to request a delay to the start of the trial to get additional time to review the “enormous” amount of evidence received from the government.

A spokesman for the Federal Bureau of Investigation’s Springfield, Illinois, office referred questions to U.S. Attorney spokeswoman Sharon Paul.

Paul said in a phone interview on Tuesday that prosecutors have no update on Yingying Zhang’s whereabouts and declined to provide details of the FBI’s search efforts.