Local administration official Indah Amperawati Masdar said residents would only be allowed to return home when the hot clouds had dissipated.
Residents were also told to avoid a southeastern area 13 kilometers along a river in the direction the ash was traveling.
Also read: Volcanic Activity Picks Up on Mount Semeru in East Java, Indonesia
The majority of residents in the two villages most at risk had been evacuated, said Patria Dwi Hastiadi, a spokesperson for the Lumajang Disaster Mitigation Agency.
Locals fled on motorbikes, some three at a time with their belongings, while others helped the elderly evacuate safely. One resident was covered in mud that had rained down on him as a mix of rain and ash.
Japan's weather agency had earlier warned that a tsunami could be triggered by the eruption affecting southern islands in the country's Okinawa prefecture, Kyodo news agency reported. But Japan's meteorological agency later said no significant tidal changes were observed.
Semeru last erupted exactly one year ago, killing at least 51 people and damaging more than 5,000 homes.
That disaster left entire streets filled with mud and ash that swallowed houses and vehicles, forcing nearly 10,000 people to seek refuge.
Semeru's alert status had remained at its second-highest level since a previous major eruption in December 2020.
Indonesia sits on the Pacific Ring of Fire, where the meeting of continental plates causes substantial volcanic and seismic activity.
The Southeast Asian archipelago nation has nearly 130 active volcanoes.
Source: Agence France-Presse
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