US lawmakers, advocacy groups say American seismologist detained in China on spying charges

WASHINGTON — A Chinese-born American seismologist who conducted U.S.-funded research on detecting North Korean nuclear tests has been detained in China for nearly two years and is facing trial on espionage charges, according to his wife, U.S. lawmakers, and two hostage advocacy groups.

The case of Youlin Chen, first reported by Reuters, has added further tension to the already strained relationship between the United States and China as President Donald Trump seeks to stabilize ties following last year’s trade conflict.

Secretary of State Marco Rubio designated Chen, 54, as “wrongfully detained” on March 19, making his release a priority for the U.S. government. The Trump administration has avoided a public announcement about the case to allow room for diplomatic efforts aimed at securing his freedom, according to Chen’s wife, Yufang Rong.

A U.S. official familiar with the matter said the administration remains focused on obtaining Chen’s release from what it described as an unjustified detention. The official spoke on condition of anonymity due to the sensitivity of ongoing diplomatic discussions.

Chen, who became a U.S. citizen in 2011 and lives in Boston, Massachusetts, is currently the only American held in China who has been officially designated by the United States as wrongfully detained, according to his wife and hostage advocacy groups.

Rong said she was informed by the White House and the State Department that Trump raised her husband’s detention during his May state visit to Beijing and discussed the matter with Chinese President Xi Jinping. Xi reportedly promised to look into the case, but Rong said no action has followed.

A U.S. official did not confirm whether Trump directly discussed Chen with Xi but said the two leaders maintain a strong personal relationship and that the case is only one part of the broader U.S.-China relationship.

In an interview with Reuters, Rong said she fears Chinese authorities have already decided the outcome of the case before Chen’s trial begins. Espionage convictions in China can carry severe penalties, including life imprisonment or, in especially serious cases, the death penalty.

“I believe they will convict him no matter what, and the trial will be behind closed doors,” Rong said.

The Foley Foundation, a hostage advocacy organization monitoring Chen’s case, believes he is among at least 12 Americans being unjustly held by China, including individuals affected by travel restrictions known as exit bans, said Elizabeth Richards, the group’s director of hostage advocacy.

The White House said Trump remains committed to bringing detained Americans home. Deputy White House press secretary Anna Kelly said the administration has helped reunite more than 100 individuals with their families during Trump’s current term.

The Office of the U.S. Special Presidential Envoy for Hostage Affairs and the Chinese embassy did not immediately respond to requests for comment.

Research on Nuclear Test Detection Under Scrutiny

U.S. embassy officials have visited Chen several times, but Chinese officials have been present during those meetings, limiting his ability to speak openly, Rong said. She added that a Chinese lawyer she hired was not allowed to meet Chen until more than 13 months after his detention.

Chinese authorities have questioned Chen more than 100 times about his research into the seismic signals produced by North Korean nuclear tests, according to Rong.

Eric Lebson, a former U.S. national security official whose hostage advocacy group Global Reach is advising Chen’s family, said he believes China may be seeking to use Chen’s expertise to improve its ability to hide underground nuclear tests through a technique known as decoupling.

The technique involves detonating a nuclear device inside a large underground cavity to reduce the strength of seismic waves, making the explosion more difficult to detect.

The Trump administration accused China in February of attempting to conceal a low-yield underground nuclear test in 2020 using such methods. China, which has signed but not ratified the Comprehensive Nuclear-Test-Ban Treaty, has denied conducting any nuclear test.

Lebson said Chen works for a U.S. government contractor but has never held a U.S. security clearance or worked on classified projects.

His research on seismic patterns from North Korean nuclear tests was funded by the U.S. State Department and the Air Force Research Laboratory, Lebson said. The studies were conducted with Chinese academic collaborators, relied on publicly available Chinese data, and were accessible online.

A December 2020 paper reviewed by Reuters analyzed the seismic characteristics of North Korea’s six known nuclear tests and examined ways to distinguish nuclear explosions from earthquakes. The document stated that it was prepared for the State Department’s arms control bureau and approved for public release.

Human rights groups have warned that China’s state secrets laws allow authorities broad discretion to classify previously public information as national security secrets, potentially placing individuals at risk for using or sharing open-source data.

Arrested Before Returning to the United States

Chen was arrested by Chinese state security officers on November 5, 2024, at Beijing International Airport while preparing to return to Boston after visiting family members and giving lectures at two Chinese universities, according to Rong and Lebson.

Rong said Chen initially endured harsh detention conditions, including being forced to sit on a hard stool for long periods without being allowed to stand, read, or exercise. She also said he was unable to receive medication for diabetes and other health issues.

Since then, Rong said it has been difficult to determine the conditions of his detention. She said Chen has lost between 30 and 40 pounds (13.6 to 18.1 kilograms), receives inadequate meals with limited protein, fruits, and vegetables, and has access only to poor-quality medication.

Chen was formally charged with espionage on May 1, 2025, but has not yet faced trial. The case could receive renewed attention during a planned visit by Xi to Washington, which Trump has said may take place in September.

U.S. Senator Ed Markey, a Massachusetts Democrat who led two senators in urging Rubio in December 2025 to designate Chen as wrongfully detained, said he remains deeply concerned about Chen’s safety and well-being.

“It is my hope that increased attention on his unjust detention will force the Chinese government to do the right thing and release Dr. Chen,” Markey said. -Reporting by Jonathan Landay in Washington; Additional reporting by Michael Martina in Washington; Editing by Don Durfee and Matthew Lewis/Reuters