Indonesia’s most active volcano erupted Monday with its biggest lava flow in months, sending a river of lava and searing gas clouds flowing 3.5 kilometers (more than 2 miles) down its slopes on the densely populated island of Java.

The rumbling sound could be heard several kilometers (miles) away as Mount Merapi erupted, sending hot ash 600 meters (nearly 2,000 feet) into the sky.

Ash blanketed nearby towns, but long-established evacuation orders are in place near the volcano, and no casualties were reported.

It was Merapi’s biggest lava flow since authorities raised its danger level last November, said Hanik Humaida, the head of Yogyakarta’s Volcanology and Geological Hazard Mitigation Center.

She said the lava dome just below Merapi’s southwest rim and the lava dome in the crater both have been active since the end of July.

The southwest rim dome volume was estimated at 1.8 million cubic meters (66.9 million cubic feet) and about 3 meter (9.8 feet) tall before partially collapsing Monday morning, sending pyroclastic flows traveled fast down the southwest flank at least twice.

Smaller pyroclastic flows of searing gas and lava traveled up to 1.5 kilometers (a mile) southwest at least twice more during the day.

The 2,968-meter (9,737-foot) peak is near Yogyakarta, an ancient city of several hundred thousand people embedded in a large metro area on the island of Java.

The city is a center of Javanese culture and a seat of royal dynasties going back centuries.

Merapi’s alert status has been at the second highest of four levels since it began erupting last November, and Indonesia’s Volcanology and Geological Hazard Mitigation Center has not raised it despite the past week’s increased volcanic activity.

The four levels describe eruption activity as normal, minor, moderate or major.

People are advised to stay 5 kilometers (3.1 miles) from the crater’s mouth and to beware of the peril of lava, the agency said.

A pair of ransomware attacks on sewage treatment plants in rural Maine communities demonstrates that small towns need to be just as vigilant as larger communities in protecting against hackers, local officials said.

The attacks occurred in April in Mount Desert and on the Fourth of July in Limestone, and no money was paid and no customer data was compromised, officials said Monday.

“It’s like an arms race between the good guys and the bad guys,” said Mount Desert Town Manager Durlin Lunt Jr. ”Fortunately, in this case, they didn’t get anything.”

In northern Maine, the town of Limestone was hit on a holiday.

Limestone Water and Sewer District Superintendent Jim Leighton said the control computer was hit with the ransomware attack.

The hackers couldn’t cause harm but the computer shutdown did take offline alarms to alert workers if pumps overheat or tanks are overfilled, he said.

In the end, the old, obsolete Windows 7 computer was due to be replaced anyway, he said, and it may have been a good thing because it caught the attention of rural water and sewage district operators in Aroostook County.

“It was a bad thing for us but a good thing for the county,” he said. “Everyone took notice and did things to their computers so they couldn’t be hit.”