The event was held on Saturday afternoon at Taieri College in Mosgiel. The hall was evacuated when smoke alarms were activated.
Mosgiel Volunteer Fire Brigade station officer Ben Parker said the smoke machines used in the concert hall activated the alarms.
Smoke alarms could not tell the difference between artificial smoke and real smoke, he said.
The fire crew was at the station taking a first aid course and only had to drive across the road to reach the college.
Acting event manager Molly Devine said the alarm set the event back by 45 minutes, and some flights and hotel bookings had to be cancelled to accommodate the change.
The smoke machines were turned off for the afternoon.
"Smokefree Rockquest will be truly smoke-free," Miss Devine joked to the crowd.
She was glad everyone co-operated well throughout the evacuation, and that nobody complained.
She found it funny the crew had to drive only a few metres across the road.
Aside from the interruption, the event was fast-paced and lots of fun, Miss Devine said.
Thirty bands took part in the regional heat, each playing one song under five minutes long.
Twelve of those bands would be selected for the regional final on June 25, she said.
There was also an award for the best solo/duo act, and one for the best use of Maori and Pasifica elements in a performance, such as instruments, lyrics, or dance.
Local band The Velvet Strings had just left the stage when the alarm went off.
Bassist Seth Fleming (17) said he was glad the band got to finish its song, and the members were not really sure what was happening when they left the building.
