The man told police he had found the explosives in his flat last year.
The man, from the Krasnoselsky region of the city, was unable to explain why he had not told the police about this find before his arrest on April 8.
According to police, the amount of TNT found in the raid was "a large amount, perhaps enough to blow up a car."
The police weren't able to say where the explosive could have originated or what its purpose might have been.
TNT is a yellow crystalline solid used for both military and industrial purposes.
It is made with toluene, nitric and sulfuric acids and is one of the most effective and easiest to handle of military high explosives because it is unaffected by ordinary friction or shock.
TNT is also used as an intermediate in the preparation of some dyestuffs and photographic chemicals. (SPP)