Investigators asked doctors to save and catalogue the bits of metal embedded in people who were near the double bomb blasts at the Boston Marathon on Monday, one physician said.

“They requested that any foreign bodies removed from wounds be saved, catalogued with the patient’s name and then turned over to them,” said Dr. William Mackey, surgeon-in-chief at Tufts Medical Center. “In the operating rooms last night, nurses were very careful to isolate any foreign bodies removed from wounds, put them in a specimen container with the patient’s name, and turn them over to the police.”

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Doctors from hospitals across the city, speaking at separate press conferences Tuesday, described some of the shrapnel in similar ways: Pellets, small BBs, headless nails—projectiles they believe were packed with the bombs. One physician said some patients were hit with dozens of metal bits.

“My opinion is that most of them were in the bomb,” said Dr. George Velmahos, trauma chief at Massachusetts General Hospital. “I think it’s unlikely they would be so consistent if they were pulled out from the environment.”

Dr. David P. Mooney, Boston Children’s Hospital trauma director, described deep shrapnel wounds in a 10-year-old being treated there who is in critical condition.

Dr. Ron Walls, chairman of emergency surgery at Brigham and Woman’s Hospital, gave a similar description of the items found, saying that nails about 1 centimeter long and small objects about twice the volume of BBs were removed from several patients. The items “clearly were designed to be projectiles that were built into the device.”

At Boston Medical Center, Dr. Andrew Ulrich said the shrapnel “could be described as buckshot.”

“We are used to a lot of chaos, but this was extraordinary,” said Ulrich, who received word about the blast just moments after starting his shift in the emergency department Monday. “Within minutes 8 or 10 patients arrived.”

Mackey of Tufts said that hospital admitted 10 people and operated on 8, mostly for blast-related injuries and damage to their lower legs.

At Boston Medical Center, at least two patients required amputations of both legs.

Nineteen patients, between ages 5 and 78, remained at Boston Medical. Of those, 16 were operated on, 11 with major procedures that could require follow-up surgeries. Ten patients were in critical condition as of Tuesday morning.

Velmahos, of Mass. General, said the lower limbs of some patients treated there were so severe that they were considered “almost automatic amputees,” Velmahos said. In those cases, he said, “we finished what the bomb started.”

Walls of the Brigham said one patient had an amputation below the knee and two others may still lose limbs. In all, the hospital treated 31 patients, 15 of whom were admitted. Nine were operated on and five are in critical condition. Dr. Michael Zinner, chairman of surgery said most injuries were to the lower body, though there was one significant head injury.

Mass. General treated 31 people injured by the blast, including four amputations and eight people who remain in intensive care. Several patients were transferred to Massachusetts Eye and Ear Infirmary.

Doctors and hospitals responded in force, Velmahos said. One physician came straight to the hospital to assist after running the race.

“The experience is obviously overwhelming, we are all extremely sad we are suffering emotionally from what happened to the people of Boston,” he said. “At the same time, we can’t feel but proud because the medical community here at Mass General responded.”

Matt Carroll, Beth Daley, Akilah Johnson, Kay Lazar, and Michael Levenson of the Globe staff contributed to this report. Chelsea Conaboy can be reached at cconaboy@boston.com. Follow her on Twitter @cconaboy.