Several persons have been arrested regarding suspicions of passing classified documents to China, the Justice Department announced on Monday. So far, four suspects have been detained in Virginia, Louisiana and Southern California, and among them, one official of the Defense Department in Virginia. The government has been investigating the cases for over a year before deciding to take action.

According to Kenneth L. Wainstein, the assistant attorney for national security who made the announcement during a news conference, “while there are entities from over a hundred different countries trying to get access to our secrets or our controlled technology, there are a number of countries that have proven themselves particularly determined and methodical in their espionage efforts. The People’s Republic of China is one of those countries.”

Among the suspected spies, Greg William Bergersen, 51, of Alexandria, who worked for the Defense Security Cooperation Agency, was charged with conspiracy to disclose national defense information to people not entitled to receive it, officials reported. Bergersen allegedly sent China information on sales of weapons to Taiwan.

Other men arrested for espionage were 58-year-old Tai Shen Kuo, and 33-year-old Yu Xin Kang, both from New Orleans. They were charged with cooperating with a Beijing intelligence official and could face life in prison for conspiracy to provide defense secrets to China. Assistant attorney general Kenneth L. Wainstein said about the two they were “particularly determined and methodical in their espionage efforts.”

Dongfan Chung, a 72-year-old naturalized U.S. citizen with Chinese origins, was arrested at his house in Orange, Virginia, officials reported. The man has had a 30-year career with the Rockwell International and Boeing and according to U.S. attorney Thomas O’Brien, he didn’t do it for the money, but rather out of patriotism for his motherland. The case is not related to the other three arrests made in California and Louisiana.