Authorities say Topalov, 33, could only have used a spoon to dig the hole in the ceiling of his cell, through which he made it to the roof. From there, Topalov was able to escape over the main fence.
Investigators have accused prison staff of a "dishonest or careless attitude to their work that was made use of by the prisoner Topalov," reports Sky News.
Topalov had been held since October 2011 and his case was sent to court last month, the Investigative Committee said in a statement. The Russian Federal Penitentiary Service issued a news release seeking information on Topalov's whereabouts.