There is growing concern in Indonesia that an imminent collapse of the Anak Krakatau volcano could unleash a deadly second tsunami.
Last week, the erupted of the the volcano triggered a killer tsunami which left more than 400 people dead.
Officials have raised the danger level this morning and ordered all flights in the nearby air space to be rerouted.
The threat level in Indonesia has been raised to its second highest, mandating a three-mile wide no-fly zone over the volcano.
Air traffic control AirNav said in a statement: “All flights are rerouted due to Krakatoa volcano ash on red alert.”
Last Saturday’s deadly tsunami was due to the collapse of the volcano crater during high tide.
Scientists are concerned that the Anak Krakatau volcano could completely collapse – unleashing an unprecedented tsunami “without any notice”.
Rosemarie North, from the Red Cross, told NBC News: “If the volcano collapses, you will not get much warning at all.”
The disaster last Satyrdat also took place without any earthquake activity beforehand.
Indonesia is prone to natural disasters due to its location on what is called the Ring of Fire.
The volatile region sits along plate tectonics underwater, causing earthquakes and volcanic eruptions.
Indonesia’s disaster management agency (BNPB) said that the Volcanological Survey of Indonesia had found an increase in volcanic activity.
Tourists have been ordered to stay away from the destination beaches due to the fears of an imminent tsunami.
Rudy Sunendar, the head of the energy ministry’s geology department, warned: “There’s still a chance of a landslide, even under the sea level or on the sea level.”
He added that there may be a new crater hole under the sea and that explosions are ongoing, with eruption sounds heard several times a minute.
Radar images from a Japanese Aerospace Exploration Agency satellite have shown the dramatic collapse which preceded last week’s tsunami.
The clips support claims that a landslide, most of it undersea, caused the tsunami that killed hundreds and injured nearly 1,500 people.