A medical student from China who U.S. authorities say tried to smuggle cancer research material taken from a Boston hospital out of the country has been held without bail by a judge who ruled he was a flight risk.

Zaosong Zheng, 29, who last year earned a visa sponsored by Harvard University to study in the U.S., appeared Monday in U.S. District Court in Boston.

Magistrate Judge David Hennessy ruled that evidence suggested Zheng had tried to smuggle vials of research specimens in a sock in his suitcase bound for China and granted the prosecution's request to hold him without bail.

He was arrested Dec. 10 at Boston's Logan Airport on a charge of making false statements.

Zheng stole the materials from his lab at Beth Israel Deaconess Medical Center, authorities allege.

Some vials contained a colleague's work he had replicated without the authorization or knowledge of the lab, Zheng told authorities, according to court documents.

Zheng was possibly acting on behalf of the Chinese government, the FBI said in affidavit included in court documents.

Zheng's federal public defender declined to comment outside court when questioned by the Boston Herald. A voicemail message was left with the defense attorney Tuesday.

Harvard officials told The Boston Globe that Zheng's educational exchange visa had been revoked.

Beth Israel, a Harvard-affiliated teaching hospital, has fired Zheng and is cooperating with authorities, a spokeswoman said.

"We are deeply proud of the breadth and depth of our research programs," Jennifer Kritz said. "Any efforts to compromise research undermine the hard work of our faculty and staff to advance patient care."

The investigation is ongoing, and more charges are possible, prosecutors said.

Explore further Chinese-American engineer charged with stealing GE technology

© 2019 The Associated Press. All rights reserved.