The Kilauea volcano on the archipelago of Hawaii in the United States on Thursday spewed ash as high as 30,000 feet – the biggest since the volcano first became active on May 3. AFP reported. The Hawaii Volcano Observatory warned that the activity may again become explosive, increasing the intensity of ash production and asked the residents of Hawaii to take shelter.

“We’ve had reports of light ash fall in Hawaii’s Volcanoes National Park and we expect that folks may be experiencing trace ash fall around Volcano Village,” Michelle Coombs of the US Geological Survey, said. “We expect activity could wax and wane like this in the near future.”

Schools around the town of Pahoa were closed after a spike in toxic sulphur dioxide gas levels. Pahoa fire station recorded a “red level” of sulphur dioxide, that would cause choking and inability to breathe, Reuters quoted Fenix Grange of the Hawaii Department of Health as saying. Officials have handed out around 18,000 masks to the residents to help them deal with the toxic gas, CNN reported.

On Wednesday, a 3.5 magnitude earthquake struck near the summit of the volcano, damaging roads and buildings and causing temporary disruption in power supply, ABC News reported.

The volcano began erupting on May 3, and since then more than 20 lava fissures have opened up, destroying more than two dozen homes or structures. The lava has created a 3.21-km path heading towards the ocean.