The volcano in Indonesia continued to erupt Tuesday morning, shooting ash three miles into the air and covering villages up to 15 miles away.
The 5-minute eruption was the most powerful since the volcano, which had been dormant for 400 years, came back to life last Sunday.
Witnesses said they saw an orange glow -- presumably magma -- at the foot of Mount Sinaburg in the cracks along the volcano's slopes for the first time.
"There was a huge, thunderous sound. It sounded like hundreds of bombs going off at one," said Ita Sitepu, 29, who was among thousands of people staying in crowded emergency shelters well away from the base. "Then everything starting shaking. I've never experienced anything like it."
Witnesses said ash and mud flooded into abandoned homes, while others said they saw bursts of fire and hot ash. The force of the explosion could be felt five miles away.
Some scientists are afraid that all of the current activity could be the warning signs of a much more destructive explosion within the next few weeks.
So far, more than 30,000 people have been evacuated.