Stop where the wounded poured up and onto the streets. Investigators say they found a second bomb at another station, which they defused. It was hidden under a fire extinguisher, and they say, had it gone off, the blast would have been even more powerful than the first. President vladimir putin, speaking in his hometown of st. Petersburg today said investigators would pursue all leads. Islamic extremists from the north caucasus have attacked before. Their most recent attack was in 2010 when two suicide bombers killed at least 40 people in the moscow metro. But since then, they have joined in the messy syrian civil war, and that may have put it squarely in the cross harris of isis. According to russian media, the police now think one man was responsible for this attack. A 23yearold from central asia with links to radical islamist groups. They believe he hid the first bomb and then got on the train with the other one in the backpack and blew himself up. In colombia, they are sifting for