Russia arrested a top scientist Saturday in Novosibirsk, just days after another scientist’s arrest in the same Siberian city.

According to the Russian state news agency TASS, Anatoly Maslov was arrested on suspicion of treason. Citing a source close to the investigation, TASS claims that “Maslov is suspected of providing data that is a state secret.” In addition to his position as a professor at Novosibirsk State University (NSU), Maslov, 75, is the chief researcher of the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences. His research centers around viscous gas dynamics, in which he is a well-known specialist.

Following his arrest, Maslov was transferred to a detention center outside Moscow where he awaits trial. His case is being investigated by the FSB, the Russian Federation’s primary security agency and successor to the KGB.

Maslov was arrested just days after Dmitry Kolker, another NSU scientist, was also arrested on suspicion of treason. Kolker, 54, who was a professor of physics and head of the university’s laboratory of quantum optical technologies, suffered from advanced pancreatic cancer and died Sunday at a hospital close to his detention center. Although he was alleged to have collaborated with Chinese intelligence agencies, Kolker maintained his innocence until his death.

Arrests—and ultimately convictions—for treason are rising in Russia. In May, a Russian court in Crimea sentenced a Ukrainian citizen to 11 years in prison for turning over privileged information to the Ukrainian government. Convictions for treason can carry a maximum of 20 years in Russia.