bombing injured 22 people, correspondent gavin ramjon is in london on the latest on the fifth terror attack in britain this year. >> reporter: london terror when a home made one exploded on a commuter train during a morning rush hour. >> suddenly i heard a big bang and i turn left and i saw the fire, and on my side. >> reporter: cell phone video from the subway car shows a white plastic bucket inside a shopping bag with what appears to be wires and a flame. sources tell cbs news that the improvised explosive device had a timer, and didn't fully detonate. >> we managed to pull it both ways and then, run down the street as fast as we can. >> reporter: police are scouring the scene and searching for security cameras to find out who put the bomb on board. >> there are many other inquiries ongoing with hundreds of expected involved like at tv, forensic work and speaking to witnesses. >> reporter: they shut down part of the train line and locked down the southwest london neighborhood. there were children on board when the blast went off. >> yes. unaudible. >> went flying. >> reporter: they