An Indonesian volcano, inactive for four centuries, erupted again on Monday, pitching ash two km (1.5 miles) into the air and sending nearby residents scurrying from their homes.

Villages were emptying fast near Mount Sinabung on the north of Sumatra island, leaving behind only officials from the bureau of meteorology and the police. Short-haul flights skirting the volcano were delayed.

Surono, head of Indonesia’s vulcanology center, told Reuters Monday’s eruption was more powerful than the first a day earlier.

“Earlier today was another eruption at 6.30 a.m., sending out smoke as high as two km, more or less,” he told Reuters.