The agency says the volcano may eject blocks up to 2 yards (1.83 meters) in diameter a little less than a mile (1.61 kilometer) away. The lower part of the Puna District, of which Leilani Gardens is a part, covers dozens of square miles and is home to many thousands of residents.
But scientists remain uncertain what caused Kilauea's latest buildup of molten rock and why the magma travelled so far underground to create new ground vents "when it had two release valves" already at the summit crater and at Pu'u 'O'o, said Michael Garcia, a volcano expert at the University of Hawaii.
Hawaii Gov. David Ige says a geothermal energy plant near a lava outbreak in Hawaii is accelerating its removal of stored flammable gas.
Kilauea is one of the world's most active volcanoes.
It said the "projectiles" emerging from the volcano could range from pebbles to rocks weighing several tons.
The Puna Geothermal Venture plant has about 50,000 gallons (189,270 liters) of pentane.
"If the lava column drops to the level of groundwater beneath Kilauea Caldera, influx of water into the conduit could cause steam-driven explosions", HVO warned.
Gas: Gas emitted during steam-drive explosions will be mainly steam, but will include some sulfur dioxide (SO2) as well. The Puna Geothermal Venture plant sits at the edge of the Leilani Estates residential area on Hawaii's Big Island where lava from 15 volcanic fissures has so far destroyed 36 structures, a lot of them homes, and forced the evacuation of around 2,000 residents.
Hawaii County Civil Defense says a 15th volcanic vent opened on Wednesday.
It would be "very, very hazardous" if a volcanic vent opened under the facility where the fuel is stored, the governor said.
That explosion killed one person and sent rocks, ash and dust into the air for 17 days.
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The plant, which is owned by Ormat Technologies of Reno, Nevada, is across the highway from where lava has been erupting.
A rock fall could create a dam, causing the steam to build pressure until it bursts through the dam as an explosion.
With the lava in Halema'uma'u, the walls surrounding the dwindling lake are now steep and unstable, and rockfalls are inevitable, said Don Swanson, a geologist with the Hawaiian Volcano Observatory, said at a news conference yesterday.
Scientist warned they don't know precisely when such an eruption could occur. "We expect that it's quite a rapid process, but we really don't know for certain".
Hawaii Volcanoes National Park will close Friday due to the possibility of explosive steam at the summit of Kilauea volcano, according the National Park Service.
The threat of potential explosions prompted park officials to announced the indefinite closure of most of Hawaii Volcanoes National Park starting Friday, May 11.
"It seems pretty safe to me right now but they'd know best", said Cindy Woodd, who was visiting from British Columbia, Canada. "Life and safety is what's most important".
Authorities initially ordered almost 2,000 residents to leave two communities in the Big Island's mostly rural district of Puna last Thursday. Authorities went door-to-door in Lanipuna to get people out of their homes on Tuesday.
"Out of the island's 4,028 square miles, only less than a 10-square-mile area of Leilani Estates and Lanipuna Gardens Subdivisions in Puna is affected", a statement from the Hawaii Tourism Authority said. A resident saw the man leaving his house when he returned to retrieve personal belongings.
Some residents have refused to leave because of fears their homes will be looted.