At least nine people were killed and 47 more injured in a bomb blast Monday afternoon in St. Petersburg's subway, according to Russia's health minister. Russian authorities are investigating the explosion as a possible terrorist attack.The attack happened between two of the busiest metro stations in Russia's second biggest city, with images and video posted to social media showing a mangled carriage with its doors blown off. Russia's Anti-Terrorist Committee said a second device was found in a nearby metro station but authorities were able to diffuse it before it went off, according to the Associated Press.While Russian President Vladimir Putin was careful not to label the attack a terrorist incident earlier in the day, his Prime Minister Dmitry Medvedev didn't hold back. He said on Facebook: "All those who were injured in the terrorist attack in St Petersburg metro will receive all the medical help they need."Read more on VICE News.