Part of Manchester Arndale was cordoned off by police amid reports of a stabbing.
Accounts from the scene suggest a teenage boy has been injured.
Pictures from inside the shopping centre show an area of the ground floor by the Corporation Street entrance cordoned off.
The victim's condition is not known.
One witness told the Manchester Evening News he saw armed police at the scene and blood stains on the floor.
Two police cars were also seen parked close to the Exchange Square Metrolink stop.
The incident took place about 4.45pm today.
The witness said: "I could see armed police there. There are about five to seven police officers and two cars.
"It looks like they were taking statements from the security guards.
"I could see blood on the floor. It was cordoned off by Foot Asylum."
David Allinson, centre director at Manchester Arndale, said: "We can confirm an incident involving three individuals took place in the lower mall at Manchester Arndale on August 2 at approximately 4.45pm.
"The area was cordoned off by Greater Manchester Police but it has now been lifted.
"The situation is under investigation and we are therefore unable to comment any further at this stage."
Greater Manchester Police have been contacted for a comment.
