At least four people have been transported to the hospital from the scene with gunshot wounds.
One of the wounded is in a critical condition, Indianapolis Metropolitan Police Department (IMPD) spokesperson Genae Cook said at an early morning press briefing.
Three others were transported to the hospital with various injuries and two people were treated by medical personnel and released at the scene, Cook added.
At least eight people were killed in Thursday's mass shooting at the FedEx ground facility near Indianapolis International Airport.
Others have been travelling by themselves to hospitals in the nearby area.
Cook said the IMPD was leading the investigation into the shooting and was working with detectives from the Indiana State Police to interview witnesses at the scene and at the hospitals. The force anticipates that the FedEx building will be closed for a while as investigators gather evidence.
"We as Indianapolis members need to come together, we need to support each other and understand there are going to be people out there that are going to be emotionally upset and we need to support them regardless of any circumstance," Cook said.
"This is a tragedy. Yet through it all we will come through it."
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