Sophia Yan And Audrey Mcavoy, The Associated Press

PAHOA, Hawaii (AP) " Geologists warned Wednesday that Hawaii's Kilauea volcano could erupt explosively and send boulders, rocks and ash into the air around its summit in the coming weeks.

The risk will rise as lava drains from the summit crater down the flank of the volcano, and explosions could occur if the lava drops below the groundwater level, the U.S. Geological Survey said.

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

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

It has destroyed 36 structures since it began releasing lava into fissures that opened in a Big Island neighborhood about 25 miles from the summit crater. There are now 14 of the fissures spread through Leilani Estates.

In the weeks ahead, the volcano could eject blocks up to two yards (meters) in diameter a little less than a mile (a kilometer) away, the USGS said. It may also send pebbles shooting into the air several miles (kilometers) away, the USGS said.

The receding lava lake resembles conditions seen before a major eruption in 1924, said Tina Neal, scientist-in-charge at the USGS Hawaiian Volcanoes Observatory.

That explosion killed one person and sent rocks, ash and dust into the air for 17 days.

No one lives in the immediate area of the summit crater. But people are continuing to visit Hawaii Volcanoes National Park, which includes the crater and surrounding region.

Park spokeswoman Jessica Ferracane said the park will be evacuated before conditions develop for an explosive eruption at the summit.

In the Lanipuna Gardens subdivision, police went door-to-door Tuesday to roust residents near two new volcanic vents emitting dangerous gases in areas where lava has poured into streets and backyards.

Authorities previously ordered nearly 2,000 residents to leave Lanipuna and neighboring Leilani Estates in the mostly rural district of Puna. But some ignored the order and stayed to watch over their property.

The emergence of the two new vents prompted Hawaii County to issue a cellphone alert ordering stragglers in the Lanipuna Gardens neighborhood to get out immediately. Police followed up with personal visits.

Officers found a number of people still at their residences but there were no sign of holdouts later, said Talmadge Magno, administrator for Hawaii County Civil Defense.

Edwin Montoya, 76, had planned to stay to care for animals and keep looters away from his family's property in Leilani Estates. He was forced to evacuate after the new fissures emerged, including one just a mile (1.6 kilometers) away.

"I'm in my truck right now on my way up the road," he said. "The police came down here and made me."

Both communities are in a forested, remote part of the Big Island on the eastern flank of Kilauea volcano, which has been erupting continuously since 1983.

In recent years the volcano has mostly released lava in hard-to-reach areas inside a national park or along the coastline. But last week, vents popped open and released lava, gas and steam inside neighborhoods.

There's no indication when the eruption might stop, or how far the lava might spread.

Authorities urged Scott Wiggers to evacuate, but he refused.

"I'm in the safest part in the subdivision. There's no threat to my house whatsoever," said Wiggers, a tour guide.

Wiggers said he wasn't leaving his home on the outskirts of the evacuation zone because he worried that if he did, he wouldn't be able to get back in. But he's prepared in case the situation takes a bad turn.

"I am packed. My truck is loaded. I'm not a dumb-dumb. If I see a threat, I'm out of here," he said.

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Associated Press journalists Caleb Jones and Jennifer Sinco Kelleher contributed to this report.