A bushfire which started on Defence land in South Australia last weekend is under investigation by the Defence Department.

The fire broke out in the Cultana Training Area near Whyalla during hot and windy conditions last Saturday.

It began on a firing range and burnt through more than 50 hectares of grass and scrub.

About 30 Country Fire Service (CFS) volunteers tackled the fire.

CFS regional commander Bluey Devine said the fire might have started after ammunition was fired in the warm, windy conditions.

“The Department of Defence are investigating the actual cause,” he said

“We initially expected that it was caused by some ordnance but that hasn’t been confirmed.

“It [the temperature] was probably low 30s but, because of the slightly increased wind speeds, the fire did get up and move and obviously burnt around 50 hectares.”

The investigation comes after New South Wales authorities concluded the State Mine bushfire burning near Lithgow was started during explosives training on army land.