MOSCOW, April 5. /TASS/. Up to 200 people could have been caught in the epicenter of a potential second blast at Ploshchad Vosstaniya station in downtown St. Petersburg had the attempt not been foiled, station’s inspector Albert Sibirsky told the Rossiya 24 TV channel on Wednesday.

"I was inspecting the station, found an object and reported about it in time. That was at a transfer point between two lines where there are always large crowds of people, anywhere from 150 to 200 riders," he said.

A source in the Russian National Guard press service said earlier on Wednesday that an improvised explosive device found at the subway station contained one kilogram of TNT. It was defused by experts from the National Guard’s engineering and technical department.

An explosive device went off on a subway train travelling between the Sennaya Ploshchad and Tekhnologichesky Institut stations on Monday afternoon. A source in the law enforcement agencies said the explosives were set off by a suicide bomber. Russian Health Minister Veronika Skvortsova said on Tuesday that the terrorist attack had left 14 people dead.