A Chinese citizen was taken into federal custody over the weekend, becoming the third scientist within a week to face allegations of illegally importing biological substances into the United States.
Third Chinese citizen arrested
Authorities arrested Chengxuan Han on Sunday at Detroit Metropolitan Airport, charging her with smuggling restricted items across international borders.
Investigators allege Han mailed four separate shipments containing biological specimens linked to roundworms from China to recipients associated with a University of Michigan laboratory.
These deliveries occurred between September 2024 and March 2025, according to the court filings.
Initially, Han reportedly denied involvement, telling investigators she had never sent any such parcels.
Later, she changed her account, claiming the contents were ordinary plastic cups.
Eventually, court records show, she acknowledged shipping the packages and admitted they contained biological samples obtained during her doctoral research in Wuhan, China.
Her attempts to enter the United States earlier this year also attracted attention.
In March 2025, Han’s visa application was denied when she struggled to answer questions during her consular interview due to limited English proficiency, which is a requirement for the process.
However, within two weeks, she reapplied and was successful. This time, Han was able to clearly discuss her academic history, her current field of study, and her future plans.
Prosecutors also claim Han misled border officials regarding the contents of the packages she sent.
Court records reveal that when investigators attempted to inspect her phone during questioning, they discovered the device had been reset just three days before her arrival in the U.S.
Chinese citizen duo arrested for smuggling
The arrest of Han follows closely on the heels of charges filed against two other Chinese nationals with connections to the same university lab.
Authorities announced last week that 33-year-old Yunqing Jian, a postdoctoral researcher, and 34-year-old Zunyong Liu had been implicated in a plot to bring into the United States a dangerous pathogen.
Fusarium graminearum is a biological agent infamous for causing significant agricultural losses across the globe.
Federal prosecutors claim the substance, which causes severe illness in livestock and humans when ingested, was concealed in small packets and transported by Liu when he entered the United States from China in July 2024.
According to officials, Fusarium graminearum can lead to vomiting, liver toxicity, and reproductive harm.
Crops such as wheat, corn, barley, rice, and maize are particularly vulnerable to this pathogen, which has been responsible for billions of dollars in damages annually.
Authorities also assert that Jian has a history of covertly bringing biological materials into the country.
According to the criminal complaint, she communicated to Liu that she previously carried a pathogen hidden in her shoe during a 2022 visit to the U.S.
“Electronic evidence also shows that Jian has been involved in smuggling packages of biological material into the United States on prior occasions,” the complaint notes.
In one instance, authorities say Jian coordinated with another contact in China to send her a book that had a small bag containing the pathogen hidden inside, with the shipment occurring in early 2024.
Investigators have not publicly disclosed whether the pathogen in that package was intercepted.
Arrested researcher part of CCP
According to the criminal complaint, Jian had received government funding from China to pursue research involving Fusarium graminearum while still living there.
Her boyfriend, Liu, works at a Chinese university and specializes in the same pathogen.
Text messages between the couple reportedly included discussions about the exchange of biological samples and shared laboratory research ahead of Liu’s arrival in the United States.
In a quote from U.S. Attorney Jerome Gorgon Jr., he stated, “The alleged actions of these Chinese nationals, including a loyal member of the Chinese Communist Party, are of the gravest national security concerns.”
The FBI noted that when Liu landed in Detroit in July 2024, his luggage contained suspicious plant-based materials.
Initially, he told Customs and Border Protection agents that he didn’t recognize the samples.
However, during further questioning, the Chinese citizen changed his account and claimed he brought the materials to support ongoing research at the University of Michigan.
Agents also discovered a scientific paper saved on Liu’s mobile device titled Plant-Pathogen Warfare under Changing Climate Conditions.
This document, authorities believe, could point to a broader intent behind the smuggling of harmful agents into the U.S.
Text messages from the week before Liu’s travel reveal further context. In one message, his partner allegedly said: “It´s a pity that I still have to work for you,” an indication that Liu may have been directing her involvement in the lab’s activities from abroad.
When FBI agents visited Jian at her lab in February, she was asked directly whether she was helping Liu conduct work involving the pathogen.
Her reply was, “100% no.” But digital records told a different story. According to investigators, her communication history demonstrated that she had indeed been researching the organism before Liu came to the U.S.
Officials also said they recovered a signed statement from Jian’s phone that demonstrated her allegiance to the Communist Party of China.
