BOSTON, MA - APRIL 16: Debris and litter cover an empty street near the scene of a twin bombing at the Boston Marathon, on April 16, 2013 in Boston, Massachusetts. Three people are confirmed dead and at least 141 injured after the explosions went off near the finish line of the marathon yesterday. The bombings at the 116-year-old Boston race, resulted in heightened security across the nation with cancellations of many professional sporting events as authorities search for a motive to the violenc
(ABC NEWS) -- In the hours since twin explosions rocked the Boston Marathon, doctors at two Massachusetts hospitals said some of their most critical patients had sustained lower extremity injuries from debris.
Dr. Ron Walls, chair of emergency medicine at Brigham and Women's Hospital, said doctors did not identify any shrapnel, such as ball bearings, but saw a lot of "street stuff" that had injured their patients.
"Rocks, bits of metal, soda cans, anything that is really close to a blast like that can be fragmented," he said. "Everything we saw was ordinary material that could have been propelled by the device."
Of the 31 patients who were transported to the hospital after the blast, nine are in critical condition and one person has "life-threatening" injuries, Walls said.
It was a similar scene at Massachusetts General Hospital, where trauma surgeon Dr. Peter Fagenholz said he found "a lot of small metal debris" in victims.
Of the 29 patients he said were seen at the hospital, eight were in critical condition.
"The most common serious injuries are combined lower extremity injuries," he said, which included bone and soft vascular trauma.
Fagenholz said several amputations had been performed at the hospital today and he had seen at least one ruptured ear drum.
"A number of patients will require repeat operations tomorrow and serial operations over the next couple of days," Fagenholz said.
While the gravity of the injuries caused by the blast was "depressing," Fagenholz said the team of doctors were focused on caring for the victims.
"This is work," he said. "When this happens, we just go to work."
On a public school holiday in Boston, children were also hit hard by the explosions.
An 8-year-old boy was among the dead, law enforcement sources told ABC News.
The death toll had risen to three people hours after the explosion, while at least 133 others were injured.
Some of the youngest victims were taken to Boston Children's Hospital, where officials said their conditions ranged from good to serious.
Among those being treated was a 2-year-old boy with a head injury who was admitted to the hospital's Medical/Surgical Intensive Care Unit, officials said, while a 9-year-old girl with leg trauma was in the operating room.
Other injuries included a 7-year-old boy who was being seen in the emergency room for a minor leg injury and a 12-year-old with a femur fracture, hospital officials said.
The 42-year-old parent of a patient was also being treated in the emergency department and three additional patients were in good condition, according to the hospital's evening update.
At Tufts Medical Center, nine people were being treated for "significant but not life-threatening injuries," ABC News' Boston affiliate WCVB reported.
Four of the surgical cases were serious orthopedic and neuromuscular trauma to the lower legs, with open fractures, while other patients suffered shrapnel wounds and ruptured eardrums, hospital officials said.