Officials did not have an update on the official's condition.
The official was injured when Mostert's Ford mounted the walls.
Two other trackside officials were forced to jump for cover.
V8 Supercars officials are yet to release Saturday's rejigged qualifying schedule.
It marked Mostert's second horror crash in three years on the mountain.
Mostert emerged unscathed when he made heavy contact at Reid Park with his Ford in 2013 practice in his Bathurst 1000 debut.
Last year, he won the Great Race with Paul Morris in a famous last-to-first effort.
"First of all, we hope Chaz is alright. He's got to get back on the horse, but it's a pretty powerful horse," two-time Bathurst champion Russell Ingall told the Seven Network. "This may re-live memories (of previous crash for Mostert)."
- AAP