The flash flooding, which struck the Sentani district of Jayapura Regency, was triggered by torrential rainfall followed by landslide.[3] The event occurred around 21:30 WIT (12:30 UTC) on 16 March, and sudden influx of water was expected to have originated from the Cyclops Mountains, which according to BNPB spokesman Sutopo Purwo Nugroho was likely caused by a landslide forming a dam blocking the headwaters of a river, which then burst resulting in the torrential flow.[4] The floodwaters swept away with it significant amounts of material, including uprooted trees and boulders.[5] An increase in the water depth of the local Kemiri River was reported shortly afterwards, resulting in buildings near the river being inundated.[6] Jayapura regent Mathius Awoitauw stated that the flooding was caused by environmental damage in the Cyclops Mountains.[7]