Private forensic investigator Paul O’Sullivan has been released on R10 000 bail..
The volcano in the Pacific island's East New Britain region began spewing rocks and ash in the early morning hours, ABC radio reported.
A witness told ABC the island's Rabaul Volcanological Observatory did not order evacations. The rumbling of the volcano could be heard in the background as she spoke.
Australia's Qantas airline said it would re-route some of its scheduled flights over the island.
Volcanic eruptions are common in the Pacific island. In 1994 Mount Tavurvur destroyed the town of Rabaul.