POSTED: Tuesday, April 16, 2013 - 8:00am
UPDATED: Wednesday, April 17, 2013 - 3:01pm
NBC NATIONAL NEWS — Federal, state, and local investigators continue their search for clues this morning as they work to determine who planted two explosive devices near the finish line of the Boston Marathon.
At least three people were killed.
More than 140 were injured, some critically.
Several blocks around the marathon finish line remain closed, classified as a crime scene, with investigators there working around the clock.
The two explosions, about 12 seconds and 50 yards apart, shattered windows and sent runners, spectators and officials scrambling for safety.
Doctors say they are treating wounds from the blasts' impact and flying debris.
"Bone injuries, soft tissue injuries and vascular injuries to the lower extremities," said Dr. Peter Fagenholz.
The FBI is leading the investigation.
Evidence collection teams have been brought in from New York.
At the White House, President Obama vowed it will be a swift and thorough search for whomever planted the devices.
"We will find out who did this, we will find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice," he vowed.
Police questioned a man who was injured and being treated in a Boston hospital, but investigators say he is not considered a suspect nor a person of interest.
Overnight, police were seen leaving the apartment of the man that was being questioned.
One official said it's too early to know one way or the other about him and that he could have been an innocent bystander.