Bali is bracing for an even larger, possibly explosive eruption, of Mt Agung after a massive 30-minute tremor inside the crater last night.
Late yesterday the largest seismic energy since Mount Agung started rumbling in early September occurred and lasted for 30 minutes.
Over 800 flights have been canceled since Bali airport closed on Monday morning, disrupting the plans of more than 120,000 passengers.
Travellers said the earliest flights to get out of Bali were on Saturday and Sunday.
Government volcanologist Gede Suantika said the mountain was in a critical phase and the observatory post near the summit may be evacuated.
“The activity of Mt Agung is now entering a very critical phase for a bigger eruption,” Mr Suantika said.
“There are two possibilities. First, the magma will fill the crater and flow out or it will come out as an explosion.
Asked when it would happen Mr Suantika said: “Soon. I can not be sure, but maybe in hours, not days because it is already erupting.
“We are just waiting for the big one.”
Villagers in the 10km exclusion zone have been told to leave and have gone to shelters.
Mt Agung’s last major eruption in 1963 killed more than 1600. That eruption lasted for more than a year.
A potential tropical cyclone was adding to the uncertainty for travelers stranded in Bali.
A slow-moving and deepening low to the west-south-west of Bali is dragging the ash cloud across Bali and Denpasar airport and it is expected to keep the airport shut at least for at least another 24 hours.
Tropical cyclone Cempka it is overriding normal locals winds that may have blown the ash cloud in the opposite direction.
Stranded passengers, particularly the elderly, are also now worried about running out of medications.
A number of stranded passengers are taking to a bus-ferry service that will take been to Surabaya for about $20 and from there flights to Jakarta, Singapore or Kuala Lumpur and other international destinations.
But many may find they are not covered by their travel insurance.
The forecast for Wednesday is for the wind conditions to remain the same, from the northeast, blowing the ash cloud over the airport and Denpasar.
However late Wednesday there may be a change to winds from the north-west which may help the situation.
Ash has been falling at the airport for over 48 hours and will require cleaning up before any airline operations can resume.
Airlines are offering credit vouchers and the ability to change travel dates to people who want cancel or modify travel plans to Bali. Some, such as Jetstar and Virgin Australia, are offering flights to alternative destinations such as Thailand and Fiji without additional charges.
Other vulcanologists have said it could take longer for the volcano to explode but there are fears it is following the pattern similar to a 1963 eruption that killed 1600 people.
The Association of Asia Pacific Airlines said airlines across South-East Asia were providing various forms of assistance to passengers such as offering to waive rebooking charges or offering credits which could be used to purchase flights to alternative destinations.
“All affected airlines are closely monitoring developments, including updates provided by the Indonesian authorities, meteorological service providers and the Volcanic Ash Advisory Centre for the region which is based in Darwin, Australia,’’ it said in a statement
“The timing of the reopening of Denpasar airport will very much depend on changes to the prevailing weather conditions, including the North Easterly winds which have spread the volcanic ash clouds which emanated from Mount Agung to cover an extended area of Bali including the airport location.
“ In addition, the relevant air navigation service provider will need to be satisfied that the related air navigation corridors can be made available for use by airline operators.
“The final decision to operate rests with individual airlines, based on comprehensive risk assessment methodologies.
“Different airlines may reach different conclusions depending on specific operational factors, such as the duration of the proposed flight, the availability of suitable alternate airports in case of unplanned diversions, and company-specific factors including the availability of crew resources at various airports.”