Russia on Thursday announced that it has launched a criminal case against an unnamed American suspected of espionage.
In a statement, Russia's Federal Security Service said the individual "is suspected of collecting intelligence information on biological topics directed against the security of the Russian Federation."
"The Federal Security Service of the Russian Federation initiated a criminal case against a US citizen on the grounds of a crime under Article 276 of the Criminal Code of the Russian Federation ‘Espionage,’" it added.
Information about the nature of the allegations was not immediately available.
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It also is unclear if the American is currently being detained.
A State Department spokesman told Fox News Thursday that it is "aware of unconfirmed reports of an investigation regarding a U.S. citizen in Russia," adding "we are looking into the matter and will continue to monitor the situation closely."
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News of the investigation comes exactly six weeks after WBNA player Brittney Griner was freed from Russia in a prisoner swap for convicted Russian arms dealer Viktor Bout.
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Paul Whelan, another American imprisoned in Russia, was not a part of that swap in December.
He has been jailed on espionage charges that his family and the U.S. government have said are baseless.
Fox News’ Ryan Gaydos and Nick Kalman contributed to this report.