The two sailors allegedly sent a blueprint for a radar system, technical manuals for vessels, operational plans for military exercises in the Indo-Pacific and details of defensive weapons to Chinese intelligence officers, the Justice Department said. Attorneys for the two sailors could not be immediately reached Thursday afternoon.

“These arrests are a reminder of the relentless, aggressive efforts of the People’s Republic of China to undermine our democracy and threaten those who defend it,” Suzanne Turner, assistant director of the FBI’s Counterintelligence Division, said in a statement. “The PRC compromised enlisted personnel to secure sensitive military information that could seriously jeopardize U.S. national security.”

The Navy did not immediately return a request for comment and service records on both men. The arrests come months after an alleged Chinese spy balloon was detected flying over the United States, prompting Secretary of State Antony Blinken to postpone a trip to Beijing in February. While Blinken eventually traveled to China in June, alleviating a diplomatic row between the two countries, tensions have persisted.

The alleged espionage also comes after a 21-year-old airman leaked hundreds of classified U.S. military documents on Discord, a chat platform popular with gamers, including assessments of the war in Ukraine and Beijing’s ability to deploy a high-altitude spy drone.

Both sailors arrested Wednesday had security clearances. It was not clear if either service member knew about the other’s actions.

“The People’s Republic of China’s continuing ability to exploit vulnerabilities, particularly financial vulnerabilities, of the cleared community is of serious national security concern as it puts our ability to protect these national secrets at an ongoing risk,” said Bradley Moss, an attorney specializing in national security and security clearance law.

In the first case, Jinchao Wei, also known as Patrick Wei, was arrested Wednesday when he showed up for work at a naval base in San Diego. He was charged with four counts related to leaking sensitive information, including the crime of espionage. It’s the sixth time that statute, under U.S. Code Section 794, has been charged across the country in the last six years, according to the Justice Department.

Wei, a 22-year-old active-duty machinist’s mate, started communicating with a Chinese intelligence officer in February 2022 about the amphibious assault ship he worked on, the U.S.S. Essex, and other ships, federal authorities alleged. Wei and the Chinese intelligence officer agreed to delete conversation record and make sure their communications were encrypted, authorities added.

Since March 2022, Wei told the agent about where certain Navy ships were located and sent images and footage of the Essex for thousands of dollars, according to the indictment. In one case, for $5,000, he sent roughly 30 ship manuals that described damage controls and systems operations, authorities alleged. The indictment in the case alleges he was told at least 10 of the manuals were useful to the Chinese officer.

Wei also sent photos of military equipment after the intelligence officer asked for details about a U.S. Marines warfare exercise, and later another 26 manuals about the power structure of his and other Navy vessels, which showed what the Navy called “critical technology,” the indictment alleged. Wei also sent a weapons system manual for the Essex and other ships, knowingly violating the International Traffic in Arms Regulations, the indictment added.

The other service member indicted, Wenheng Zhao, also known as Thomas Zhao, was arrested for sending sensitive military information to someone posing as a maritime economic researcher in exchange for money. The person was actually a Chinese intelligence officer, according to the Justice Department, but had allegedly told Zhao they wanted the information for investment research. Zhao, 26, worked at Naval Base Ventura County in Port Hueneme.

Zhao allegedly sent photographs, recordings and videos of blueprints of a radar system on a U.S. base in Japan and other military information to the intelligence officer beginning in August 2021, the indictment alleged. The information included the location and timing of Naval movements for a large-scale military exercise and allegedly continued until at least May of this year, the indictment added.

The Chinese agent paid Zhao nearly $15,000 for the information while making sure he destroyed any evidence, the indictment alleged.