Stranded travellers face insurance trouble

Thousands of travellers left stranded after volcanic ash from the eruption of Mount Agung halted flights in and out of Bali may not be insured even if they had purchased a policy.

A number of Australian travel insurers issued statements saying their customers would only be covered if they had bought policies up to nine weeks ago - before the Indonesian government issued an alert for the volcano.

Some companies have stipulated a cut-off coverage date of September 22 which is when the volcano alert was first raised to a level four, suggesting an eruption was imminent.

Others are refusing to cover those who purchased a policy on or after September 18 when the alert was raised from normal to "vigilance".

A number of insurance companies, however, have stated they'll allow travellers to claim if they purchased their insurance before November 22.

Geologist Mark Tingay was in Bali celebrating his 40th birthday when Mount Agung majorly erupted on Saturday. He managed to fly back to Australia on Sunday night.

Dr Tingay said while he was sympathetic to those who were left with no insurance the risk presented by the volcano had been known for some time.

"It really was very widely documented, the authorities have done everything they can to alert people of the risk," the Adelaide University academic told AAP on Tuesday.

"It is terrible that people are stuck without travel insurance though - that is a major issue."

Dr Tingay bought his travel insurance well in advance - when he purchased his plane tickets to Bali.

But he suspects many people probably purchased a policy because of the volcano alert.

"Then they'll be caught out by the fine print," he said.

Travellers have been advised to check their insurance websites to see if they're covered by their policy.

Thousands of Balinese locals forced from their homes around Mount Agung have been left stranded in evacuation centres for months as they await the all clear to return.