MOUNT MERAPI, Indonesia — Indonesia’s most volatile volcano erupted Tuesday after scientists warned that pressure building beneath its dome could trigger the most powerful explosion in years. A 2-month-old baby reportedly died as panicked villagers fled the area.

Smoke poured out of Mount Merapi, obscuring its cone, according to footage from the private station, MetroTV. Up to 20 people were injured by the hot ash spewing from volcano, said an AP reporter who saw them being taken away for treatment. One burn victim’s skin was coated in the gray powder, which also blanketed vehicles in the area.

Some 11,400 villagers who live on the 9,737-foot high mountain were urged to evacuate, but only those within four miles of the crater were forced by authorities to do so. Most of those who fled were the elderly and children. Some adults said they decided to stay to tend to homes and farms on the fertile slopes.

There are fears that the current activity could foreshadow a much more destructive explosion in the coming weeks or months, though it is possible, too, that the volcano will settle back down after a slow, long period of letting off steam.

As they contended with the volcano, Indonesian officials were also trying to assess the impact of Monday’s 7.7-magnitude earthquake off the coast of Sumatra, about 800 miles  from Merapi. The temblor caused a tsunami that left hundreds dead or missing on a string of remote islands.

MetroTV reported that the baby died when a mother ran in panic after the eruption started. Its report cited a local doctor and showed the mother weeping as the baby was covered with a white blanket at a hospital. The report did not make clear if it was a boy or girl.

Subandriyo, the chief vulcanologist in the area, said the eruption started just before dusk Tuesday. The volcano had rumbled and groaned for hours.

"There was a thunderous rumble that went on for ages, maybe 15 minutes," said Sukamto, a farmer who by nightfall had yet to abandon his home on the slopes. "Then huge plumes of hot ash started shooting up into the air."

Scientists have warned the pressure building beneath the dome could presage one of the biggest eruptions in years at Merapi, literally Mountain of Fire, which lies on the main island of Java, some 310 miles (500 kilometers) southeast of the capital Jakarta.

The alert level for Merapi has been raised to its highest level.

"The energy is building up. … We hope it will release slowly," government volcanologist Surono told reporters. "Otherwise, we’re looking at a potentially huge eruption, bigger than anything we’ve seen in years."

In 2006, an avalanche of blistering gases and rock fragments raced down the volcano and killed two people. A similar eruption in 1994 killed 60 people, and 1,300 people died in a 1930 blast.

This vast archipelago is prone to earthquakes and volcanic activity due to its location on the so-called Pacific Ring of Fire — a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.

There are more than 129 active volcanos to watch in Indonesia, which is spread across 17,500 islands.

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Associated Press writer Irwan Firdaus contributed to this report from Jakarta.