Hawaii County and Hawaii Volcanoes Observatory officials are warning the public that a collapse of the Pu’u ‘O’o crater floor on Kilauea volcano’s East Rift Zone has triggered increased earthquake activity and may signal an impending lava flow outbreak.

Christina Neal, scientist-in-charge at the observatory, said that seismicity was occurring as far east as Highway 130, and warned residents of lower Puna to remain alert and watch for further information about the status of the volcano at www.hawaiicounty.gov/active-alert.

“An outbreak of lava in a new location is one possible outcome,” Neal said in a statement. However, she cautioned, “it is not possible to say with certainty if or where such an outbreak may occur, but the area downrift (east) of Puʻu ʻOʻo is the most likely location, as this is where seismicity and deformation (change in ground surface shape) have been concentrated overnight.”

The HVO daily update said that at about 2 p.m. Monday, scientists witnessed “a marked increase in seismicity and ground deformation” at Pu’u ‘O’o.

“A few minutes later, a thermal webcam on the rim of the Pu’u ‘O’o crater showed the first of two episodes of crater floor collapse; the second collapse began at 3:20 p.m. and lasted about an hour,” the update said.

A magnitude 4.2 earthquake offshore of Puʻu ʻOʻ0 occurred at 2:39 a.m. today, the largest of a series of recent quakes along the rift zone, scientists said. The U.S. Geological Survey website shows dozens of tremors of magnitude 2.5 or greater over the last day.

County officials have closed the Kalapana lava viewing area amid the possibility of an eruption, and posted security to keep unauthorized people out of the area.

“We don’t want people hiking in that area, which is downslope from the rift,” Parks and Recreation Deputy Director Maurice Messina said in a news release. Messina said the lava viewing area can draw 500 to more than 2,000 visitors.