All but a few of the estimated 500 inhabitants of Kapoho and adjacent Vacationland development are now believed to have fled their homes, an agency spokesman said.
County officials said in a news release that there is no access to Kapoho and Vacationland along Highway 132 or Highway 137 because of the lava flow.
County Managing Director Wil Okabe said his own vacation home in Kapoho Beach Lots is also threatened.
Hawaii Civil Defense Service officials said they went through the neighbourhood to warn residents this was their last chance to evacuate before their final escape route was cut off by lava.
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Seven people have been killed and 20 hurt after a volcano near Guatemala City exploded in a fiery display of ash and lava. The Guatemalan military said it was providing assistance including clearing volcanic ash from the airport's runway.
Lava from a fissure near the volcano entered Kapoho Bay overnight, forcing billowing clouds of steam into the atmosphere as hot lava hit the cool water of the Pacific Ocean. In addition, most of Vacationland and all but the northern edge of Kapoho Beach Lots have been inundated with lava.
Officials warned residents about the presence of laze, a potentially risky mix of hydrochloric acid, steam and tiny glass particles in the air.
Between May 4 and Monday, there have been almost 10,000 earthquakes, according to the U.S. Geological Survey.
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The Fallout universe seems to have been steadily heading in this direction with Fallout 4 and the mobile game Fallout Shelter. Vault 76 dates back to Fallout 3 and is mentioned in both the base game and in the Mothership Zeta DLC pack.
So too have airborne volcanic glass fibers, called "Pele's hair", wispy strands carried aloft by the wind from lava fountains and named for the volcano goddess of Hawaiian myth.
In addition, at over four weeks, this eruption has lasted longer than the 1955 and 1924 eruptions, the USGS said. He faces charges that include refusing to evacuate and reckless driving.
Most of Hawaii Volcanoes National Park has been closed since May 11 because of earthquakes and continuous explosions from the volcano's summit crater.
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