The offspring of Indonesia’s infamous Krakatoa volcano erupted on Sunday, spewing a towering volcanic ash cloud some 3,000 meters (9,800 feet) into the sky.

Mount Anak Krakatoa, which means Child of Krakatoa, belched thick ash over the strait that separates the islands of Java and Sumatra, forcing authorities to warn nearby residents to wear masks outside.

“We are still recording continuous eruptions with thick clouds towering at between 500 to 3,000 meters from the peak,” Deny Mardiono of Indonesia’s Geological Agency told AFP. Authorities ordered people to stay out of a two-kilometer exclusion zone around the volcano, which is currently graded at level two of Indonesia’s four-tiered volcanic alert system.

“People, including tourists, should adhere to the recommendation from the Geological Agency, which prohibits anyone to be within a two-kilometer radius from the crater,” he added.

Anak Krakatoa has erupted at least 21 times in recent weeks but Sunday’s eruption was the largest yet, Mardiono said.

The volcano has been sporadically active since it emerged from the sea at the beginning of the last century in the caldera formed after the 1883 eruption of Mount Krakatoa. That disaster was one of the deadliest and most destructive in history with an estimated 35,000 people killed.

Anak Krakatoa last erupted in 2018, generating a tsunami that killed 429 people and left thousands homeless.