PAHOA, Hawaii (AP) — Geologists say the Big Island’s Kilauea volcano could erupt explosively and send boulders, rocks and ash into the air around its summit caldera in coming weeks.

The U.S. Geological Survey said Wednesday the risk will rise if the lava drops below the groundwater level beneath the summit’s caldera or craterlike basin. That’s because an influx of water inside could cause steam-driven explosions.

The agency says the volcano may eject blocks up to two yards in diameter a little less than a mile away.

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It may also send pebbles shooting into the air several miles away.

There’s also potential for ash, steam and sulfur dioxide emissions.

Kilauea is one of the world’s most active volcanoes.

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It has destroyed 36 structures since it began releasing lava into a Big Island residential neighborhood last week.

On Tuesday, police went door-to-door to evacuate residents near two new vents emitting dangerous volcanic gases in Hawaii.

The vents emerged on Tuesday near the spots where lava has been pouring into streets and backyards for the past week.

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Authorities initially ordered nearly 2,000 residents to leave two communities in the Big Island’s mostly rural district of Puna last Thursday.

But the new vents prompted Hawaii County to issue a cellphone alert ordering stragglers in the Lanipuna Gardens area to get out immediately. Police followed up with personal visits.

Fourteen vents have opened since the current lava breakout began. The lava has destroyed 36 structures.