On Tuesday morning an explosion happened in a subsidiary premise of an apartment house in Kirov area of St.-Petersburg. Under the preliminary version, the reason of explosion could become an explosive, including a grenade. Incident happened nearby 9:10 a.m. in the house №6 in Korneyev Street. As the press-service of the Emergency Situations RF, explosion occurred in a room for sanitary technicians on the first floor of 10-storeyed apartment house. The area of a room is 20 square meters. Three persons suffered. Physicians estimate condition of two of them as heavy. Forty-year old man is hospitalized in extremely grave condition, 27-year old one - in heavy is delivered to the hospital 26. The third victim - 37-year old man - is in moderately grave condition, he is also hospitalized to the hospital 15. - Despite of all mentioned above, as it's already became accepted, neither consequence, nor mass-media mention a word "act of terrorism", - editor-in-chief of FORUM.msk Anatoly Baranov commented. - Probably, "casual handling with grenade" will be the final version. It remains behind brackets what a grenade did in the room of sanitary technicians.