Officials have warned of potentially intensified 'explosive activity' amid an eruption at Kilauea volcano in Hawaii.
US Geological Survey (USGS) has raised its aviation warning level from orange to red - meaning a major eruption is imminent or underway.
The main ash cloud has reached as high as 10,000 to 12,000 feet above sea level.
In a statement, the USGS said: "As of early this morning, eruption of ash from the Overlook vent within Halemaumau crater at Kilauea Volcano's summit has generally increased in intensity.
"Ash has been rising nearly continuously from the vent and drifting downwind to the southwest. Ashfall and vog (volcanic air pollution) has been reported in Pahala, about 18 miles downwind."
It adds: "At any time, activity may become more explosive, increasing the intensity of ash production and producing ballistic projectiles near the vent."
Activity at Halema‘uma‘u crater. Image: USGS
Communities near the volcano, which is located on Hawaii's 'Big Island', have reported ashfall.
Several areas have previously been evacuated.
The area has seen increased volcanic activity in recent days and weeks - leading to issues such as steaming fissures in the ground, and some lava flows.
While the volcanic activity has led to dozens of minor earthquakes, officials - including Hawaii Governor David Ige - have moved to reassure the public following speculation about a potential tsunami.
FALSE RUMOR: No geologic evidence for a tsunami-generating earthquake. https://t.co/RpzLAcb7A4
— Governor David Ige (@GovHawaii) May 16, 2018