"In connection with the incident in the Mozhaysky Academy in St. Petersburg, the Russian Investigative Committee's military investigation directorate for strategic missile forces opened a criminal investigation… into attempted murder of two or more persons in a generally dangerous manner," the investigators said.
According to the Russian Ministry of Defence, three people have been injured as a result of the explosion.
"At about 1:30 p.m. [10:30 GMT], in St. Petersburg, an unidentified unshelled object exploded in one of the offices of the administrative building of the Mozhaysky Military and Space Academy," the ministry said in a press release.
The ministry further added that all of the injured had already received medical care and their lives were out of danger.
В академии имени Можайского взрыв произошёл на пятом факультете. В результате обрушился лестничный пролёт, на третьем этаже сейчас заблокированы 15 человек. pic.twitter.com/Wv7Ww9EZao— 78 | НОВОСТИ (@good78news) 2 апреля 2019 г.
Earlier in the day, a representative of the regional emergency services reported about four cadets been injured as a result of the blast.
A.F. Mozhaysky's Military-Space Academy in St. Petersburg is one of the largest military education establishments in Russia.