Police cordoned off the area as the Philadelphia Bomb Squad, SWAT officers and bomb-detection dogs searched the center, The Philadelphia Inquirer reported.
The center reopened at about 1:30 p.m. after the police said the area was clear, The Philadelphia Inquirer said.
Lt. Joseph McGarrey said police evacuated the center, a popular tourist site, after a "suspicious person" dressed in camouflage was detained for questioning.
No explosives were found at the center, McGarrey said.
Ashton Seiwell, 21, a Temple University student who works for a vendor at the center, said he was there when police evacuated the area.
"I'm not really that nervous," Seiwell said as he waited to return to work. "I'm not too worried. I'm more intrigued. I just want to know what's happening."