Indonesia's most active volcano erupted on Wednesday sending a river of lava and searing gas clouds flowing 3,000 meters (nearly 10,000 feet) down its slopes. No casualties were reported.

The sounds of the eruption could be heard 30 kilometers (18 miles) away, officials said. It was Mount Merapi's biggest lava flow since authorities raised its danger level in November, said Hanik Humaida, the head of Yogyakarta's Volcanology and Geological Hazard Mitigation Center.

She also said the volcano's lava dome is growing rapidly, causing hot lava and gas clouds to flow down its slopes.

After morning rain, the ashfall turned into muck in several villages. More than 150 people, mostly elderly, living within 5 kilometers (3 miles) of the crater were evacuated to barracks set up for displaced people.

Authorities in November had evacuated nearly 2,000 people living on the mountain in Magelang and Sleman districts but most have since returned.

The alert is being maintained at the second-highest level and authorities told people to stay out of an existing danger zone around the crater.

The 2,968-meter (9,737-foot) volcano is on densely populated Java island near the ancient city of Yogyakarta. It is the most active of dozens of Indonesian volcanoes and has repeatedly erupted with lava and gas clouds recently.

Merapi's last major eruption in 2010 killed 347 people.

Indonesia, an archipelago of 270 million people, is prone to earthquakes and volcanic activity because it sits along the Pacific “Ring of Fire,” a horseshoe-shaped series of seismic fault lines around the ocean.