Steam and sulfur rises from cracks in Moku Street at the head of a driveway in Leilani Estates, Tuesday, May 8, 2018, in Pahoa, Hawaii. Police have gone door-to-door to evacuate residents near two new vents emitting dangerous volcanic gases in Hawaii. The vents emerged near the spots where lava has been pouring into streets and backyards for the past week. (Hollyn Johnson/Hawaii Tribune-Herald via AP/Manila Bulletin)
The U.S. Geological Survey said the risk will rise if the lava drops below the groundwater level beneath the summit's caldera.
An influx of water inside could cause steam-driven explosions. 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 residential neighborhood last week.
Since the eruptions began, 14 such fissures have opened in a subdivision and destroyed dozens of structures, including 26 homes.
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.
In the Leilani Estates 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 the two communities in the mostly rural district of Puna on Hawaii's Big Island last Thursday. 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.
Andrew Nisbet has no idea what happened to his house since he left it.
"My home is right in the line of the major breakouts so maybe, maybe not." he said Monday during a community meeting.
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 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.
Officials warn that lava could flow downhill and burn areas that don't currently face danger and that toxic volcanic gas could kill people, especially the elderly and those with breathing problems.
Hawaii Gov. David Ige, a Democrat, told evacuees he has called the White House and the Federal Emergency Management Agency to tell officials that he believes the state will need help to deal with the volcano.
There are 14 lava-and-gas producing fissures in Leilani Estates. But the flow of lava is not constant.