Hawaii County said steam and lava poured out of a crack in Leilani Estates, which is near the town of Pahoa on the Big Island.
Footage shown on local television showed lava spurting into the sky from a crack in a road. Aerial drone footage showed a line of lava snaking through a forest.
Lava fountains were shooting 150 feet (46 meters) in the air, and molten lava spread out over an area about 200 yards (183 meters) wide behind one house in Leilani Estates, Big Island resident Ikaika Marzo told the Honolulu Star-Advertiser .
|In this photo provided by the US Geological Survey, red ash rises from the Puu Oo vent on Hawaii`s Kilauea Volcano after a magnitude-5.0 earthquake struck the Big Island, Thursday, May 3, 2018 in Hawaii Volcanoes National Park.|
"It sounds like a jet engine. It's going hard," he said.
County, state and federal officials had been warning residents all week that they should be prepared to evacuate, as an eruption would give little warning.
The county has ordered evacuations for all of Leilani Estates, which according to the 2010 US Census has a population of 1,500.
Nearby community centers have opened for shelter.
Ranson Yoneda, the recreation director for the Pahoa District Park, was readying the gymnasium for evacuees after it was selected as a Red Cross evacuation center.
He said so far, about 15 people have arrived, some with animals, and they are hungry for information.
"They just want to know what's going on because they were told it's a mandatory evacuation," he said by telephone.
The US Geological Survey said new ground cracks were reported Thursday afternoon. Hot vapor emerged from a crack and spattering lava began to erupt.
Scientists said areas downslope of the erupting vent were at risk of being covered by lava. Leilani Estates appeared to be at greatest risk, but scientists said new vents and outbreaks could occur and it's not possible to say where.
The eruption comes after days of earthquakes rattled the area's Puna district. A nearby school was closed due to the ongoing seismic activity and several roadways cracked under the strain of the constant temblors.
The Puu Oo crater floor began to collapse Monday, triggering a series of earthquakes and pushing the lava into new underground chambers.
The collapse caused magma to push more than 10 miles (16 kilometers) downslope toward the populated southeast coastline of the island.
USGS geologist Janet Babb said the magma crossed under Highway 130, which leads to a popular volcano access point, on Tuesday night.
Hawaii County Civil Defense Agency closed the area to visitors on Tuesday and ordered private tour companies to stop taking people into the region.
Most of Kilauea's activity has been nonexplosive, but a 1924 eruption spewed ash and 10-ton (9-metric ton) rocks into the sky, leaving one man dead.
Puu Oo's 1983 eruption resulted in lava fountains soaring over 1,500 feet high. In the decades since, the lava flow has buried dozens of square miles (kilometers) of land and destroyed many homes. (AP)