The uranium, copper and gold explorer said it has been working with Primary Industries and Resources of South Australia (PIRSA) and the Environmental Protection Authority over the way materials have been disposed of at the project.

"Marathon has commenced an internal investigation into its practices to assess compliance with the Exploration Licence requirements," Marathon's chairman Peter Williams said.

"Marathon has comprehensive records and photographs of all processes undertaken. If the authorities request that further work be done, our records enable us to do it, and we will."

The announcement comes after allegations of contamination at drilling holes onsite.

South Australia's acting Minister for Mineral Resources Development Michael Atkinson has been reported as saying the possible environmental breach called for an investigation, even though the substances were not considered dangerous.

Shares in Marathon closed up 15c yesterday to $2.05 and remains unchanged in morning trade.