A potentially explosive well at a geothermal power station on Hawaii has been covered by lava from the erupting Kilauea volcano after it flowed onto the site.

Locals fear an explosion of deadly hydrogen sulphide and other gasses should the well be ruptured.

Lava has never engulfed a geothermal power plant anywhere in the world and the potential threat is untested, according to the head of the state’s emergency management agency.

However, both the covered well and another which is threatened by flowing lava “are stable and secure,” Hawaii’s Civil Defence Agency said.

David Ige, the governor of Hawaii, said the geothermal plant was “sufficiently safe” from the lava, which has burned dozens of homes.

The molten rock was expected to continue to flow across the Puna Geothermal Venture (PGV) facility, according to the US Geological Survey.

Hawaii Kilauea volcano eruption: in pictures Show all 30 1 /30 Hawaii Kilauea volcano eruption: in pictures Hawaii Kilauea volcano eruption: in pictures Channelized lava emerges on Kilauea Volcano's lower East Rift Zone on Hawaii. The USGS said on its website that "a fast-moving pahoehoe lava flow that emerged from fissure 20... continues to flow southeast," with the quickest of three "lobes" progressing at 230 yards (210 meters) per hour. AFP/US Geological Survey Hawaii Kilauea volcano eruption: in pictures Lava erupts and flows from a Kilauea volcano fissure in Leilani Estates, on Hawaii's Big Island Getty Images Hawaii Kilauea volcano eruption: in pictures A plume of ash rises from a crater in the Mount Kilauea volcano after a magnitude 6.9 earthquake struck the area, near Pahoa, Hawaii EPA/USGS HANDOUT Hawaii Kilauea volcano eruption: in pictures Kilauea has opened 14 lava-and-gas spewing fissures in total Rex Hawaii Kilauea volcano eruption: in pictures United States Geological Survey Hawaii Kilauea volcano eruption: in pictures Lava from a Kilauea volcano fissure advances up a residential street in Leilani Estates, on Hawaii's Big Island, on May 27, 2018 in Pahoa, Hawaii Mario Tama/Getty Images Hawaii Kilauea volcano eruption: in pictures A massive flow of lava consumes houses in Leilani Estates EPA/PARADISE HELICOPTERS Hawaii Kilauea volcano eruption: in pictures Lava flows past trees on the outskirts of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii. REUTERS Hawaii Kilauea volcano eruption: in pictures A plume of ash rises from Kilauea Volcano after a series of earthquakes over the last couple of days USGS/Handout via Reuters Hawaii Kilauea volcano eruption: in pictures Lava emerges from the ground after Kilauea Volcano erupted Hawaii Kilauea volcano eruption: in pictures Steam rises from a fissure on a road in Leilani Estates subdivision on Hawaii's Big Island AFP/Getty Hawaii Kilauea volcano eruption: in pictures This thermal image (looking south) shows the active overflows from the lava lake (upper left) onto the Halema'uma'u crater floor. View is toward the south. Rex Hawaii Kilauea volcano eruption: in pictures The results of the eruption from Kilauea Volcano on Hawaii's Big Island AP Hawaii Kilauea volcano eruption: in pictures Lava is seen coming from a fissure in Leilani Estates subdivision on Hawaii's Big Island FREDERIC J. BROWN/AFP/Getty Images Hawaii Kilauea volcano eruption: in pictures An aerial view of a flow of lava moves to the doorsteps of the Puna Geothermal Venture facility after a new fissure eruption within Leilani Estates sending a fast moving flow of lava began to consume homes and property, near Pahoa, Hawaii EPA/BRUCE OMORI/Paradise Helicopters Hawaii Kilauea volcano eruption: in pictures Smoke rises from the Pu'u 'O'o crater on the Kilauea volcano in Hawaii EPA Hawaii Kilauea volcano eruption: in pictures Up to 10,000 people were ordered to evacuate as flows of red lava entered residential areas Reuters Hawaii Kilauea volcano eruption: in pictures A fissure erupts in Leilani Estates, one of the communities most vulnerable to Hawaii's Kilauea volcano AP Hawaii Kilauea volcano eruption: in pictures Smoke billows from Pu'u 'O'o crater on the Hawaii's Big Island EPA Hawaii Kilauea volcano eruption: in pictures Remote image released by U.S. Geological Survey, shows a new lava fissure on Kilauea Volcano's lower East Rift Zone on Makamae and Leilani Streets USGS via AP Hawaii Kilauea volcano eruption: in pictures Kilauea volcano's Pu'u O'o vent on Hawaii's main island AP Hawaii Kilauea volcano eruption: in pictures Lava flows over a road in the Puna District as a result of the eruption from Kilauea on Hawaii's Big Island Byron Matthews via AP Hawaii Kilauea volcano eruption: in pictures Kilauea volcano erupts AP Hawaii Kilauea volcano eruption: in pictures Lava flowing over Mohala Street in the Leilani Estates area near Pahoa Hawaii Electric Light via AP Hawaii Kilauea volcano eruption: in pictures An aerial view of a massive surface flow entering the sea at Malama Flats EPA Hawaii Kilauea volcano eruption: in pictures Satellite photo provided by DigitalGlobe shows lava coming out of fissures caused by Kilauea AP via DigitalGlobe Hawaii Kilauea volcano eruption: in pictures The fissure complex, pictured in the upper right, continues to feed a meandering lava flow (in the center). into the Pacific Ocean in southeast of Pahoa during ongoing eruptions of the Kilauea Volcano in Hawaii REUTERS Hawaii Kilauea volcano eruption: in pictures Lava erupts from a Kilauea volcano fissure Getty Images Hawaii Kilauea volcano eruption: in pictures A U.S. National Guard soldier (R) takes photos as lava erupts and flows from a Kilauea volcano fissure in Leilani Estates, on Hawaii's Big Island Getty Images Hawaii Kilauea volcano eruption: in pictures This is a horizontal, royalty free stock photograph of a glowing lava tube opening from the Kilauea volcano in Volcanoes National Park on the Big Island of Hawaii. Photographed with a Nikon D800 DSLR camera. Getty Images/iStockphoto

Authorities shut down the plant after Kilauea began a once-in-a-century scale eruption on 3 May.

They removed 60,000 gallons of flammable liquid and deactivated wells which tap into steam and gas deep in the Earth’s core.

Magma from Kilaueau’s summit lava lake has drained and flowed around 25 miles (40km) east of the volcano, bursting out of the ground through about two dozen giant cracks or fissures near the plant.

An aerial view of a flow of lava moves to the doorsteps of the Puna Geothermal Venture facility after a new fissure eruption within Leilani Estates sending a fast moving flow of lava began to consume homes and property, near Pahoa, Hawaii (EPA/BRUCE OMORI/Paradise Helicopters)

The Israeli-owned 38 megawatt plant typically provides around 25 per cent of electricity on the Big Island, according to local power utility Hawaii Electric Light.

Last week, Operator Ormat Technologies Inc said there was no above-ground damage to the plant, but it would have to wait until the situation stabilised to assess the impact of earthquakes and subterranean lava flows on the wells.

Hawaii volcano: Aerial footage shows rivers of lava reaching the ocean

Over the weekend, there were more than 250 earthquakes at Kilauea’s summit, with four explosions on Saturday sending ash as high as 12,000-15,000 feet, officials said.

US Marine Corps and National Guard helicopters are on standby for an air evacuation if fissure activity cuts off Highway 130, the last exit route for up to 1,000 coastal residents.

More residents in some sections of the Leilani Estates neighbourhood were ordered to immediately evacuate shortly before 8pm on Sunday “due to a fast moving lava flow from Fissure 7”, a statement from the civil defence agency said.

Lava from a Kilauea volcano fissure advances up a residential street in Leilani Estates, on Hawaii's Big Island (Mario Tama/Getty Images)

Authorities have also warned the volcano is now spewing out vog, or volcanoc smog.

It is created when vapour, carbon dioxide and sulphur dioxide from Kilauea mix together.

The grey haze can cause coughing, sore throats, headaches and other symptoms in generally healthy people, and it can be even more problematic for those with respiratory problems.