PVMBG reported that an eruption at Semeru was recorded at 0725 on 18 January and lasted almost four minutes.
A gray ash plume rose around 400 m above the crater rim and drifted SW and W.
Ash plumes rose 300-400 m and drifted W and N during 19-21 January.
The Alert Level remained at 2 (on a scale from 1-4); the public was warned to stay 1 km away from the active crater and 4 km away on the SSE flank.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)