The researcher from the Russian city of Novosibirsk was accused by the service of providing the U.S. Department of Defense top secret information regarding advanced types of solid rocket fuel, the Moscow Times said Wednesday.

Korosbeinichev's lawyer said that, according to FSB officials, the charges were dropped due to a lack of evidence.

The chemist is the director of a lab at the Institute of Chemical Kinetics and Combustion, where his efforts are focused on combustion and flames.

By closing its investigation into Korosbeinichev, the service has now ended two espionage investigations into national researchers.

The Times said that in late 2000, the service had dismissed charges against Pacific Oceanological Institute head Vladimir Soifer after a 17-month investigation.