One of the world’s most active volcanoes erupted again early Monday. Lava fountains stretched more than 200 feet and a cloud of toxic gas rose over Hawaii, officials said.

Kilauea’s eruption began around 2 a.m. and “may continue for a while,” said Ken Hon, senior scientist at the Hawaiian Volcano Observatory.

According to the US Geological Survey, there were no immediate threats to infrastructure.

Hon said elevated levels of “vog” – a potentially harmful mix of water vapor, carbon dioxide and sulfur dioxide – were expected in areas south and west of the volcano in the coming days. Although heavy volcanic smog is expected, he urged residents to stay indoors.

At 4:30 a.m., lava fountains reaching 262 feet high were seen, the agency said, and “lava bombs” and other molten material were ejected from the crater floor. By 5:30 a.m., the agency estimated that 400 hectares of the caldera floor was covered in lava.

The volcano in Hawai’i Volcanoes National Park on the Big Island has been erupting since 1983. The most recent outbreaks occurred in June and September, Hon said.

Dozens of homes were destroyed after an eruption in 2018 that forced thousands to flee.