Indonesia’s Anak Krakatau volcano expanded by 32.8 hectares after recent eruptions produced lava flows, while satellite imagery detected two new land formations nearby, the country’s Geology Agency said.

The increase was found by comparing Sentinel satellite images from August 8 and September 15, Reuters reported. Anak Krakatau erupted for 25 hours from September 4 to 6, sending lava toward the northwest, west and southwest.

Imagery from September 23 showed one new formation about 760 metres northwest of the volcano’s coastline and another about 495 metres to the southeast. The agency said more analysis is needed to determine whether they are new eruption centres.

The eruptions sent ash over Jakarta and surrounding areas, forcing several airports to close. More than 340,000 travellers were affected, with 2,961 flights cancelled, delayed or diverted.

Anak Krakatau is one of about 130 active volcanoes in Indonesia, which sits on the Pacific Ring of Fire. The volcano means “child of Krakatau” and emerged a century ago from the site of the 1883 eruption that killed more than 36,000 people.