The Latest on the eruption of Kilauea volcano on Hawaii's Big Island (all times local):
Hawaii officials are checking with residents to see if they need help as fast-moving lava approaches a mostly rural part of the Big Island.
Hawaii County Civil Defense said Friday that police, firefighters and National Guard troops are securing the area and stopping people from entering.
About 40 homes are now isolated in the newly affected area east of Leilani Estates and Lanipuna Gardens — two neighborhoods where lava has destroyed 40 structures over the past two weeks.
Officials are using helicopters to assess how many people are still in the newly threatened area.
County officials had been encouraging residents in the district to prepare for potential evacuations. The county is now asking people to stay put and wait for further instructions.
Wendy Stovall of the Hawaiian Volcano Observatory says geologists are trying to pin down the precursory signals for Kilauea's explosions to give people better warning.
A large explosion at the summit this week spewed a 30,000-foot (9,100-meter) ash plume into the sky.
Scientists believe steam and hot rock explosions will continue.
Scientists say that a sample from a fissure in a subdivision shows that fresher, hotter magma could produce faster lava flows.
As of Friday, 22 fissures have opened and 40 structures have been destroyed.
A volcanologist says there's just no telling when Kilauea's volcanic activity will subside.
Janine Krippner of Concord University in West Virginia says much of what is happening is below the earth's surface on Hawaii's Big Island, making it tough for experts to say for certain.
Charles Mandeville of the U.S. Geological Survey's volcano hazards program says Kilauea has produced similar eruptions several times in the past 2,000 years.
Ash coming out of the volcano's summit can be a nuisance for area residents, though people are unlikely to be at risk as the park surrounding Kilauea has been closed and evacuated.
Mandeville says a larger hazard is lava flowing and hot, toxic gases coming out of open fissure vents in the middle of housing and infrastructure.