While there is no confirmation yet on whether the blasts were the result of a terrorist attack, Stevenson said something he saw before the race was unusual.

„At the starting line this morning, they had bomb sniffing dogs and the bomb squad out there,“ he said. „They kept announcing to runners not to be alarmed, that they were running a training exercise.“

He added, „I‘ve run a lot of races like this one, but I never saw bomb dogs at the starting line of any running event. It led me to believe that something like (a bomb detonation) might have happened.“