In the initial confusion of the day, it appeared as Davis spoke that another explosion may have already happened. The commissioner said officials were treating an incident at the John F. Kennedy Presidential Library, in the Dorchester neighborhood several miles from the marathon finish line in the Back Bay, as potentially related to the other explosions.
According to subsequent news reports, what occurred at JFK Library was a fire in a mechanical room. The cause remains unknown.
Authorities around the city are active Monday evening on multiple fronts: checking the marathon course and other areas for explosives, tending to the injured, helping people who are trying to locate loved ones, and launching an urgent hunt for whomever set the explosives.
Separately, law enforcement officials said people should call 800-494-TIPS with any tips related to the crime.
With the two explosions in close proximity to each other, and the possibility that the JFK library incident may be linked to the bombings, the possibility rises that the perpetrators planted other explosives across a much wider area, say homeland security experts. Indeed, another device was discovered and exploded by authorities Monday.