Chinese authorities said they arrested a Northern California scholar earlier this month, accusing him of espionage and endangering national security.

U Min Zin was taken into custody on June 3 at Kunming Changshui International Airport in Yunnan Province, southwestern China, according to a New York Times report. Details about the arrest are still unknown. Min Zin was traveling for academic purposes.

Earlier this week, Foreign Ministry spokesperson Lin Jian said in a news conference that the United States Consulate General in Guangzhou was notified of Min Zin’s arrest, the New York Times said.

The arrest came after President Trump met with Xi Jinping in China to stabilize U.S.-China relations and manage disputes over Taiwan, Iran and regional security.

“We are aware of reports regarding a U.S. citizen detained in China,” a State Department official told SFGATE. “Whenever a U.S. citizen is detained, we work to provide the appropriate consular assistance. However, under federal privacy law, we are unable to comment further at this time.”

Min Zin was a doctoral student at UC Berkeley, where he also obtained a master’s in Asian studies and political science, the university confirmed with the Los Angeles Times. His studies center on Myanmar and Chinese foreign policy, according to his published works.

He is a founder and executive director of ISP Myanmar, a Thailand-based think tank focused on Myanmar and regional policy issues. Min Zin was also a student activist in Burma’s 1988 democracy movement, according to the Journal of Democracy.

His activism got him kicked out of high school, and he went into hiding to avoid arrest, according to a 2008 interview. He fled to Thailand in 1997 and spent years working as a journalist, later writing for publications such as the New York Times and Foreign Policy.

“If I could return home today, I would go. I belong to Burma. My family is there. I want to dedicate myself to establish good journalism and education, because I realize that education is the key to developing Burma,” Min Zin told the Jakarta Post in 2008.

He applied to UC Berkeley at age 35.

“We are aware of news reports regarding this matter,” a UC Berkeley spokesperson told the L.A. Times. “Our thoughts are with Min Zin and his family at this difficult time.”