LUMAJANG, Indonesia — The death toll from the eruption of Indonesia's Mount Semeru has risen to 39, authorities said Wednesday, as rescuers scrambled to retrieve more bodies under the threat of further volcanic activity.

The highest mountain on the island of Java thundered to life on Saturday, ejecting volcanic ash into the sky and raining hot mud on villages as thousands of panicked people fled their homes.

"The search and rescue team found four more bodies today," Indonesia's search and rescue agency said in a statement.

Another injured victim died in hospital on Tuesday, it added, pushing the death toll up from 34 to 39.

A spokesperson for the agency said 12 people were still missing.

The disaster blanketed villages in grey ash and forced more than 4,000 people to flee to temporary shelters.

Evacuees had been complaining of coughing, chest infections and diarrhea, according to medics at shelters in Lumajang district.

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Others expressed relief at making it out alive and being reunited safely with loved ones.

Sutimah, a 45-year-old woman taking refuge at a shelter, said her husband escaped the mudflows just in time.

"My husband was working as a miner. If he had run away seconds later, he would have been killed. His colleague, a truck driver, was swept away by the mudflow," she told AFP.

Rescuers have been braving dangerous conditions in their search for bodies buried under the mud and rubble of collapsed houses.

The head of the country's volcanology agency said there was also still the potential for "secondary eruptions" and warned people to stay away.

Indonesia has more than 130 active volcanoes and sits on the Pacific Ring of Fire, where the meeting of continental plates causes frequent volcanic and seismic activity.

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