Hikers and climbers in New Zealand have been warned to stay away from Tongariro National Park’s Mount Ruapehu, which has been featured in “The Lord Of The Rings” movies. Earthquake and volcano monitoring service GNS Science elevated the alert for Mount Ruapehu, saying the mountain’s crater lake temperature had doubled in the past few weeks.

“Volcanic gas measurements indicate an increase in the amount of both carbon dioxide and sulphur dioxide output ... Seismic activity at Mount Ruapehu is usually dominated by volcanic tremor. Since the volcanic earthquakes in late April the seismicity has been dominated by volcanic tremor at varying levels. The level of tremor has increased but is not exceptional in terms of the last few years,” Geoff Kilgour, a GNS Science volcanologist said, according to the New Zealand Herald.

The temperature of the crater lake reportedly rose from 77 degrees Fahrenheit to 115 degrees Fahrenheit since mid-April. The alert level has been raised to “heightened unrest” from “moderate.” Mount Ruapehu last erupted in 2007.

The Department of Conservation warned hikers to steer clear of the Summit Hazard Zone, within a mile of the center of the crater lake.

“Recent visits to the volcano have confirmed an increase in the output of volcanic gas,” GNS Science said, according to Reuters.

Ski areas, other facilities or roads on Mount Ruapehu or in Tongariro National Park have not being affected by this warning.