The eruption began on July 7 sending a large ash, gas and steam plume to high altitudes and caused significant ashfall in communities.
Several villages near the base of the 1800m high mountain have been under evacuation orders because of the impact of ash on food and water supplies, the ABG statement said.
The villagers were ordered to make their way to either Torokina or Wakunai stations.
Preliminary information from an observation by the Rabaul Volcanological Observatory has confirmed that while the summit area remains obscured, there had been a pyroclastic flow, but that this was small and confined to riverbeds.
This flow includes lava, ash and hot gases, and it means rivers originating from the volcano are contaminated.
Relief efforts are being coordinated through Disaster Management Teams with food, water and shelter supplies having been transported to Wakunai station yesterday and the same material will be airlifted to Torokina today.
The Health Emergency Operations team is working to detect any outbreak of waterborne and airborne diseases in both areas.
A team is being set up to oversee health promotion and health awareness activities in the camps the evacuees have been sent to.
A total of 18 schools across the Torokina and Wakunai districts have been affected by ash and a number have been evacuated.