No one has been arrested, said police, who were still investigating.
Police officials checked through police reports, at The Inquirer's request, to find the flash-mob injuries.
The mob formed when an estimated 2,000 youths, mostly African American, sprang up on South Street on the first night of spring. They were summoned by messages on the Internet and on cell phones.
As traffic snarled, businesses along South Street locked their doors, and some restaurants kept their patrons inside to ensure their safety.
The flash mob had three Center City precursors on March 3, Feb. 16, and Dec. 18.
The injured 13-year-old boy, whose name was not released, was at 11th and South Streets at 2:55 a.m. March 21. He was "jumped and beaten by a large group of males," police said, "15 to 20 people."
The boy suffered cuts to his right eye, upper right cheek, and the right side of his forehead, police said.
He was taken to Children's Hospital of Philadelphia with his mother, police said.
The injured officer was near Fifth and South Streets when she began running to assist other officers trying to control the mob, police said.
She fell and cut both knees and suffered scratches on her hands. She also injured her left side, police said. No one had attacked the officer, and she did not seek medical assistance, police said.
After the South Street incident, many people asked whether there was a racial component to the flash-mob attacks. Mayor Nutter's spokesman called the notion "ridiculous."
Taylor said she did not think that she and her boyfriend had been targeted because they are white. The 13-year-old boy who was beaten is African American, according to the police report.
A 32-year-old South Philadelphia auto-repair worker said he believed that a friend was hit in the head March 20 by a teenager at Bliss restaurant, on Broad Street a few blocks north of South, because he is white.
Assistant District Attorney Angel Flores, who prosecuted youngsters from the Center City flash mobs, said none had expressed a desire to harm white people.
He added that African Americans were no happier to see the flash mobs than white people, and that some even had been victimized, including a man who was knocked down by a mob but didn't report it.
Perhaps the motivation was not so much race as class, said Nathan Shapiro, 24, a University of Pennsylvania graduate dental student, who told The Inquirer that he also had been attacked during the flash mob but had not notified police.
"Maybe I got attacked because I look like a student," a person with more means than the crowd of youngsters, said by community leaders to be from impoverished neighborhoods.
Regardless of the motivation, the attack was "shocking and terrifying," Shapiro said, "just so random and unprovoked."
As he was walking with two friends around 11:15 p.m. March 20 at 11th and South Streets, Shapiro, of Charlottesville, Va., saw hundreds of teenagers heading toward him.
At one point, out of the corner of an eye, he noticed someone got "too close."
"Before I knew it," he said, "I felt this mind-blowing pain in my right jaw from a punch, and when I looked to see who did it, I couldn't find anybody."
Shapiro said that his mouth had swelled up, but that he hadn't lost any teeth. He didn't file a police report because he could never say who had done it, he said.
The attack, Shapiro added, has made it "really difficult not to let it affect how I feel about this city.
"I feel like it could still happen again at any moment and not much will be done to effectively prevent it."