Shoppers have been evacuated from an Adelaide Hills Woolworths store after a large fire broke out on Sunday afternoon.

Country Fire Service and Metropolitan crews were called to the Stirling store just after 2:15pm, with about 85 firefighters working to contain the blaze.

No one has been injured.

SA Police and SA Ambulance Service are also at the scene and a CFS spokesperson said a large area has been cordoned off due to the thick, acrid smoke in the area.

Executive manager operations with CFS Cameron Devey said the cause of the fire has not yet been determined.

“There are reports that some aerosol canisters and the like were exploding, and very early indications were that it was a very large fire,” Mr Devey said.

“We are yet to identify what has caused the start of this blaze.

“We will work with SAPOL and fire investigators throughout the evening, when it’s appropriate for them to go in, but it’s too early to determine the cause at this stage.”

Mr Devey said roads in the area would be closed into the evening and power outages would affect Stirling into the night.

He said fire crews will remain at the scene for some time, but thankfully some smaller businesses inside the complex had been saved.

“Nearby and adjoining businesses have been saved, critical infrastructure at the moment such as the Telstra exchange has been saved, as well as the Post Office,” he said.

“We also want to acknowledge the community impact that this will have, we know there will be people expecting to work tomorrow who may be unable to do so.”

David Alderdice had been shopping in the supermarket when he heard the alarms going off.

“Then all of a sudden a PA system comes out with ‘evacuate, evacuate, this is not a drill’ and everyone starts pouring out of the building,” he said.

Mr Alderdice said when he came out to the carpark, the road was no longer visible.

“It was only a matter of minutes, the roof had collapsed in by that stage as well.”