Kilauea volcano erupted overnight, and subsequent lava flow destroyed four homes and prompted evacuations on the Big Island of Hawaii, according to the local civil defense agency.

"The flow has advanced 1,000 feet in less than one hour," Hawaii County Mayor Harry Kim tweeted Saturday.

Kim's spokeswoman, Janet Snyder, said four people were airlifted from the Malama Ki Place area while three others sheltered in place overnight before fleeing Saturday. "Everybody accounted for and out of the area as of this a.m.," she said via email.

Kilauea let off a "short-lived steam explosion" around midnight, producing an ash cloud that rose an estimated 10,000 feet, the Hawaii County Civil Defense Agency said in a statement Saturday.

Another "brief explosive eruption" was reported at 7:45 a.m. Saturday, according to the National Atmospheric and Oceanic Administration. "Additional explosions are possible at any time with little warning," the NOAA said in a statement.

Authorities said gas emissions from Kilauea were a serious threat for "downwind" locals. "Residents are reminded to protect themselves from ash fallout by remaining indoors," the civil defense agency stated.

Lava from Kilauea's fissure 20 flowed west of Pohoiki Road, near Malama Ki Place, where those homes were taken out, officials said. The flow isolated about 40 residences, authorities said. Residents should be ready to flee at a moment's notice, they said.

Officials warned residents of Kamaili Road in the Puna district Saturday evening that they needed to leave immediately due to brush fires caused by lava.

Also Saturday, a man on the third-floor balcony of a home on Noni Farms Road was hospitalized after he was struck Saturday by "lava spatter," Snyder said.

"It hit him on the shin, and shattered everything from there down on his leg," Snyder, who said she was informed of the situation by fire officials, said in an email Saturday evening.

There have been no deaths reported in the current eruption period. But lava has destroyed more than two dozen homes, officials have said.

Lava flow was less than a mile from a coastal highway, 137, and could reach it by day's end, the civil defense agency stated in an update. The roadway will be closed if lava crosses, according to the statement.

Officials warned people to stay away from any beach where fresh lava reaches the Pacific. This can create hazardous "laze," or plumes made up of a mix of hydrochloric acid gas, steam, and tiny volcanic glass particles, according to the U.S. Geological Survey.