Security agents are investigating a Russian scientist for allegedly trying to smuggle out of Russia materials that could be used in building a biological or bacteriological weapon, the scientist and his co-workers said Friday.

Oleg Mediannikov is the latest in a growing number of academics and scientists who have been targeted by Russia's main security agency, the Federal Security Service, for allegedly misusing classified information, revealing state secrets or, in some cases, espionage.

Mediannikov, a biologist at Moscow's Gamaleya Institute of Epidemiology and Microbiology, told The Associated Press that he was traveling to France in December to bring vials of a non-dangerous typhoid vaccine to colleagues when he was stopped by customs officials at Sheremyetevo Airport.

The samples were confiscated and sent to a government laboratory for testing, but Mediannikov said he was allowed to travel to Marseilles, then returned to Moscow without further incident.

In February, as he tried to travel to Africa on a tourist trip, he said he was denied permission to leave at Moscow's Domodedovo Airport. His passport was confiscated and was returned to him two months later, he said.

In June, he said he was notified he was under investigation for smuggling materials that might be used for preparing weapons of mass destruction — a charge he said could result, if convicted, in a sentence up to seven years in prison.

Mediannikov said he had the necessary documentation and permits for the samples at the time they were confiscated. He also said that the directors of the Gamaleya Institute have asked him to resign, but he has refused.

"Logically, this shouldn't be happening at all, but it is and why it is remains a complete mystery for me," he told the AP. "I really hope that wiser heads will prevail."

Anatoly Osipenko, deputy director of the Gamaleya Institute, accused Mediannikov of violating Russian customs law by not declaring the samples when he was leaving the country.

A duty officer at the Federal Security Service refused to comment on the investigation, saying all questions should be submitted in writing.

Didier Raoult, a French biologist with the University of the Mediterranean, said Mediannikov had been to France three times in the past without incident.

"We've been working with the Gamaleya Institute for 15 years and we've never had any problems. Even when we were working in communist times," Raoult said.

Earlier this year, customs officials banned exports of blood samples and other biological materials from Russia; the Health Ministry, however, said the decision by customs' officials concerned only major shipments of biological materials and would not affect ordinary patients.

The Health Ministry and other Russian officials gave no reason for the decision, but it appeared to reflect official suspicions about Western companies' involvement in the sensitive sphere of health care amid a deepening chill in ties and accusations of European and U.S. meddling in Russia's affairs.

Health Minister Mikhail Zurabov later said that new rules governing the export of human blood and tissue would soon be set.

It was not immediately clear whether the rules had been issued, or whether they would concern the samples Mediannikov was carrying.

The investigation highlighted the chill that has fallen over Russian scientific research under President Vladimir Putin, a former KGB officer.

In 2004, physicist Valentin Danilov was convicted of spying for China and sentenced to 14 years in prison for providing allegedly sensitive information that he said had been published in part in publicly available scientific magazines. The same year, arms control researcher Igor Sutyagin was convicted of treason for selling information on nuclear submarines and missile-warning systems to a British company that Russian investigators claimed was a CIA cover.

Last month, the Federal Security Service said it was dropping its investigation of two physicist-brothers who published a booklet last year that outside experts determined, the service said, contained classified information "related to the development of armaments."