russia's launched a massive police response in the wake of twin bombings in volgograd. 5200 police officers and government troops have detained dozens of people but none is considered a suspect in either of the two attacks in the last 48 hours. one blast tore through a trolley bus on monday. the first explosion gutted a railway station sunday. the blast was captured on surveillance cameras. at least 30 people were killed in 48 hours. volgograd is a transportation hub that connects to sochi 400 miles to the north. the site of the olympic games, of course. but the international olympic committee says it's confident russia can keep the games safe and secure. nbc's jim maceda joins us live in sochi. jim, what is the latest on the investigation there?