Rescuers in fire-retardant suits are battling to dig out two men trapped in a bunker on Indonesia's Mount Merapi.
The fierce heat from the volcano's recent eruptions has melted shovels and the tyres of diggers as rescuers try to dig through two metres of rubble.
The two men have been trapped in the bunker since Wednesday night, when they fled there to escape a burning cloud emitted by the simmering volcano.
The bunker's door is blocked by a large hot boulder, rescuers say.
Mt Merapi, in the centre of the island of Java, spewed out clouds and ash on Wednesday after weeks of intermittent activity.
"We have so far dug one metre deep. It's very difficult because the bunker was covered with rocks and sand," local official Suryadi told news agency AFP.
Rescuers are working amid the threat of further eruptions
"We hope there won't be any victims but we have no idea whether or not they are alive. We hope that they are," another official said.
He said the bunker was equipped with oxygen, but its electricity had been knocked out in the explosion.
Wednesday's explosion has caused scientists to warn the volcano, which killed more than 1,300 people during an eruption in 1930, may erupt imminently.
Some 15,000 villagers who had been housed in makeshift camps during earlier activity since the middle of May had begun returning home on Wednesday.
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