More than 50 firefighters worked to contain St Johns fire

Fire crews continue to mop up a fire which ignited just after 2pm on Tuesday and burnt about 40 hectares of grass and stubble.

According to a CFS spokesperson, the fire began following machinery movement between the quarry and Rockbrook Road, St Johns, near Koonunga.

It is understood SA Police have since spoken to the operator.

The blaze resulted in 50 firefighters from 11 appliances and one bulk water carrier in attendance.

Four farm fire units also assisted on the scene.

The CFS spokesperson also said two bombers were brought in with only one water drop made.

While no one was injured or infrastructure damanged, a watch and act message was made but revoked at about 4.30pm when the fire was contained.

The fire spread into a creek bed and parts of a nearby quarry and burnt pine trees which caused the smoke visible from Stockwell and other parts of the Barossa.