Lava from the Kilauea volcano in Hawaii has crept towards a geothermal power plant, prompting workers to shut down facilities amid fears of deadly gases.
Workers removed flammable substances and the plant's deep underground wells have been filled with cold water. They will be plugged with iron on Tuesday.
If lava flows into the wells before they are plugged, it could release lethal hydrogen sulphide gas.
The slow-moving lava entered the plant site on Monday, but has since stalled.
"It's not easy to predict where it's going to go, and when it's going to get there," Tom Travis from Hawaii Emergency Management told CBS News.
County officials said the lava was around 900ft (274m) from the closest well on Monday.
In the worst-case scenario, Mr Travis said there would be "a steam release, many chemicals, but primarily hydrogen sulphide, a very deadly gas".
Emergency workers at the plant transported 60,000 gallons of highly flammable pentane gas out of the facility as a precaution.
Located on the Lower East Rift Zone of the Kilauea volcano, the Puna Geothermal Venture (PGV) plant generates around 30% of the island's electrical power by bringing steam from the underground wells into a turbine generator.
The plant's wells run a mile deep in some areas.
Kilauea erupted at the beginning of May and the situation for residents has steadily been worsening.