Law-enforcement authorities say they believe an active terrorism cell may be operating in New York and New Jersey in connection to this weekend’s attacks, sources told NBC News. An explosion in Manhattan that injured 29 people Saturday and bombs planted in New Jersey—including one that detonated early Monday near a train station—have led officials on a hunt over the weekend to determine if the plots were connected. Heavily armed FBI agents were spotted throughout the city of Elizabeth investigating the train-station incident. Though damage was minimized after bystanders found a backpack with what appeared to be five bombs and alerted police, an attempt to disarm at least one device resulted in a non-controlled explosion. Nobody was reported injured.