SA Police say the Westfield Marion shopping centre in suburban Adelaide was locked down on Sunday afternoon after reports of fighting between two groups of young males.
SA Police Assistant Commissioner Scott Duval said the centre's management issued an evacuation alarm after reports some of the people involved had weapons, including expandable batons.
He said police conducted a thorough search of the shopping centre but have not located either of the groups.
Assistant Commissioner Duval said there was no ongoing threat to the community and they had been able to safely clear the centre.
"I would say that's it's clear from the vision this is not a random attack," he said.
"The boys would appear to be known to each other, but obviously we're still in the early days of investigation of the incident.
"The incident really involved three boys approaching another group of boys. We're not clear on the intention of that at this stage but I stress that it does not appear to be a random attack."
Police said no one was hurt as a result of the altercation between the boys, but two people were believed to have been injured during the evacuation process.
"I would encourage these boys to hand themselves into police. Perhaps they didn't intend for this to occur but they need to understand the consequences for their actions," Assistant Commissioner Duval said.
The SA Ambulance Service (SAAS) previously told the ABC that paramedics were treating two patients for non life-threatening injuries; a woman in her 70s who suffered a shoulder injury and another person with a knee injury.
SAAS said one of the patients was being transferred to the Flinders Medical Centre for treatment.
Loading...In a statement, a Westfield Marion spokesperson said the safety of their customers, business partners and people were their "highest priority".
"Our team have been providing their full support to SA Police this afternoon who attended an incident at Westfield Marion. For a brief period SA Police were in full control of the site," the spokesperson said.
SA Police have since advised it is safe for customers to leave the centre.
The spokesperson said the shopping centre will re-open for trade as normal on Monday.
'I look up and the whole store was shut'
Dale Benedict Cubar was working in a sushi store at the time and says he hid for an hour.
He says about 10 people hid alongside him.
Wendy, who was locked down inside Woolworths while speaking to the ABC, said she was at the check-out getting ready to leave the store when the shutters came down.
"There was an announcement saying there was an incident with weapons in the mall, and that the mall was in lockdown as a result," she said.
"It was all pretty fast, the shutters came down really quickly, I didn't even realise they were coming down because I was at the check-out and next thing I look up and the whole store was shut.
"The Woolworths staff have periodically updated us throughout the ordeal with information, but they don't have a lot of information."
One person told the ABC they were watching a movie when they heard a noise going off.
"And someone went out of the movies, and all of a sudden everyone just came running in and sprinting in and said run run!"
Another person said the announcement was not immediately clear.
"We didn't really know what was going on, and then people started to leave because they were a bit confused, and then it was just flooding back in, screaming."
"And we thought the people had entered the cinema to be honest so we ducked, and then I was like, we just need to run, so we ran."