Mount Merapi, Indonesia ? Rescuers dug through volcanic debris today to reach two people trapped when Indonesia’s most volatile volcano erupted, nearly enveloping a village with a searing gas cloud and forcing thousands of residents to flee.

The eruption Wednesday came just a day after officials lowered the alert level and people returned to the homes around Mount Merapi.

“The situation is … life-threatening,” said Yousana Siagian, head of the government’s Vulcanology and Disaster Mitigation Center, after the alert level for Mount Merapi was raised to its highest status again and it dumped thick ash on scores of houses.

This morning, crews struggled to reach two people trapped in an underground emergency shelter by the eruption, officials said. Five other villagers were reportedly missing.

The rescuers had been in touch with the two by cell phone. The bunkers, several of which dot the slopes of Merapi, are typically equipped with water and food.

Scientists had thought that the 9,700-foot volcano was calming down after weeks of activity when a gas cloud cracked its fragile lava dome on June 8, easing the buildup of pressure.

Indonesia's Mount Merapi spews lava as seen from Deles village, outside Yogyakarta. After the eruption early today, rescuers dug through volcanic debris to reach two people trapped in an underground bunker.

The alert level was dropped a notch on Tuesday, sparking widespread relief for people who have spent weeks in evacuation camps and were trucked home. But that quickly turned to concern Wednesday as Merapi demonstrated its famed unpredictability.

“We were very happy to go back in the morning, but as soon as we got there, we saw a massive cloud steaming toward us,” villager Edi Egan said after being trucked back to the camp. “We all decided it was time to leave.”

Up to 20,000 people live in the danger zone, taking advantage of the rich volcanic soil. By nightfall, at least 1,100 were back in camps and some 12,000 others were given orders to leave.

A superheated gas cloud nearly enveloped the village of Kaliadem, the closest residential area to the peak, only four miles away, said Siagian, the government vulcanologist.

A similar cloud killed 60 people in 1994, and about 1,300 people died when Merapi erupted in 1930.