Officials also announced a twist in the probe: Suspicious packages that were detonated out of precaution were not explosive devices after all.

Massachusetts Gov. Deval Patrick announced Tuesday that there were only two bombs — the two that exploded at the marathon, killing three people and wounding 176.

A doctor who treated some of the wounded said Tuesday the wounds were caused by shrapnel that included pellets and nails. Seventeen of the injured remain in critical condition.