Teenagers arrested over Westfield Marion Shopping Centre fight ...

Two teenagers who police say allegedly robbed a male of his clothing have been arrested after the incident sent a major shopping centre in Adelaide's south-west into lockdown yesterday. 

Police say just before 3pm on Sunday, two groups of boys were fighting in the food court of the Westfield Marion shopping centre, with reports some had weapons.

Centre management activated an alert and evacuation alarm, and the centre went into lockdown.

A number of police swarmed the centre to search for the groups involved but did not find them.

Police say overnight they arrested two boys, aged 15 and 16, and charged them with assault, affray and aggravated robbery.

Assistant Commissioner Scott Duval says a robbery sparked the brawl at Marion shopping centre.(ABC News)

Assistant Commissioner Scott Duval said the fight started when three boys approached another group of boys at the centre's food court.

"What we'll allege is it's effectively motivated by the robbery of clothing," Assistant Commissioner Duval told ABC News Breakfast.

"They were targeting clothing from one of the male victims and during that, one of the weapons were produced and that became the cause of the incident that caused Westfield Marion to effectively put their emergency procedures in place for the purpose of public safety."

He said the altercation was not a random attack.

"How that meeting occurred in the food court is still to be determined but sufficed to say the groups were known to each other," Assistant Commissioner Duval said.

Police seized two expandable batons during the pair's arrest.

Police responded to the incident at Westfield Marion.(ABC News: Briana Fiore)

"It's a baton that effectively expands, not dissimilar to what police would use," Assistant Commissioner Duval said.

"Certainly the possession of them is very concerning, that formed part of the allegation of what these boys were charged with."

The two teens will appear in the Adelaide Youth Court later today.

Assistant Commissioner Duval said police were looking for a third boy and encouraged him to hand himself to police.

“We do know his identity and we are making active enquiries to locate him," he said.

Assistant Commissioner Duval said by the time the first officers arrived, the centre had put its emergency procedures in place.

He said police would review and learn from the events, including the time it took to clear the centre and evacuate people reportedly sheltering for more than two hours in retail stores.

"There was obviously an amount of inconvenience that's caused to people but what I'd say to that is all of our actions are about ensuring public safety and nothing we'd do would ever compromise public safety," Assistant Commissioner Duval said.

"I think in terms of how long people are locked in shops, it's really about how long it takes to effectively clear the centre and do that safely.

"We can't release people while we're still in a period of response."

Assistant Commissioner Duval praised the community for cooperation during "difficult times".

"I certainly empathise with those people that were caught in shops and particularly with young children, the effect of that is well acknowledged," he said.

"But at the same time we need to make decisions that are all about people's safety."

Kris Hanna says the shopping centre operators took a cautionary approach.(ABC News: Trent Murphy)

City of Marion Mayor Kris Hanna told ABC News Breakfast the stabbing at Bondi Junction was front of mind for many people.

"And I think that's why the centre management reacted the way they did, nobody can blame them for taking a very cautionary approach," Mr Hanna said. 

"Something that would have been probably unremarkable outside a pub on a Friday night of course was highly unusual in the food court of the local mall. 

"But everybody would have had in mind the terrible [stabbing] at Bondi Junction just a short while ago so when they flashed up on screens in the mall 'armed offender', I'm sure thousands of people probably thought the worst."

A sign at Westfield's Marion Shopping Centre during the lockdown.(ABC News)

Senior Constable Matt Brown told ABC Radio Adelaide people who felt impacted by the events that unfolded at the shopping centre should seek mental health support.

"Anyone who was affected by yesterday's events, either you were at the scene when it happened or you had to go pick up a family member or friend who was working at the centre, please contact welfare services or some sort of counselling if you are feeling stressed out or anxious over what happened yesterday," Senior Constable Brown said.

"Incidents like these we just need to gather around each other and make sure everyone's OK, and be grateful that the incident was handled very safely."