Eight Indonesian airports, including two serving Jakarta, remained closed early on Monday morning because of volcanic ash from eruptions at Mount Anak Krakatau, the transport minister said.

Ash from Anak Krakatau, which sits halfway between Java and Sumatra islands, has blanketed Jakarta and several surrounding areas since it erupted late on Friday, leading to the closure of the airports for safety reasons.

The transport ministry said 170,000 people have been affected by flight cancellations.

Jakarta’s main airport will ⁠remain closed until 6 p.m. local time (1100 GMT), its operators said on Monday on Instagram.

“We cannot ascertain when this will end due to the dynamic weather,” Transport Minister Dudy Purwagandhi said in a statement on Monday, adding that the seven other airports, which included the ones serving Jakarta’s nearby provinces of Lampung and West Java, would remain closed until at least 08:59 a.m..

The volcano monitoring agency’s website showed the most recent Anak Krakatau eruption occurred Sunday at 8:23 p.m.

The agency warned on Monday that “the probability of further eruptions in the ⁠coming periods remains high.”

The eruptions have seen ash reach as high as 20,000 feet (6,000 metres) on the Java side of the volcano and 50,000 feet (15,000 metres) on the Sumatra side and some parts of Banten province in Java, meteorological agency BMKG posted on its website.

On Sunday, ⁠the disaster agency called for people to wear masks while travelling outdoors to avoid breathing in the ash. In Jakarta and Lampung, schools will use remote learning to counter health risks for students, state ⁠news agency Antara reported.

Indonesia sits on the Pacific “Ring of Fire”, where earthquakes and volcanic eruptions are frequent.

Anak Krakatau, which means child of Krakatau, began emerging a century ⁠ago from the area previously occupied by Krakatau, then known as Krakatoa. The older volcano destroyed itself in mass eruptions in 1883, which killed more than 36,000 people in a series of tsunamis.