Asbestos scare emerges as HMAS Adelaide's troubled Tonga mission concludes

Australian soldiers have been helping Tonga recover from a devastating tsunami. (Defence Department: Robert Whitmore)

Australian Defence Force personnel fear they were exposed to dangerous asbestos fibres during clean-up operations in tsunami-devastated Tonga.

Defence has confirmed members of Operation Tonga Assist discovered asbestos material while clearing debris and destroyed local infrastructure on Atata Island after the January disaster.

The revelation comes as HMAS Adelaide begins returning home from a troubled six-week deployment that saw the Navy's largest warship hit by a COVID-19 outbreak and crippling power failures on board.

Last month Navy officials suggested volcanic debris around Tonga was considered the likely cause of an initial power outage on the landing helicopter dock, which is still being formally investigated.

A COVID outbreak also hit the ship's crew while en route from Brisbane to Tonga, with at least one fifth of the crew eventually testing positive to the virus.

HMAS Adelaide was sent to Tonga to help locals. (Defence: POIS Christopher Szumlanski)

A source connected to the operation said troops were "worried" they may have been exposed to friable asbestos fibres.

"A problem with the clean-up in the last days has been the disturbance of asbestos from damaged and bulldozed structures," the official told the ABC, speaking on the condition of anonymity.

"No risk assessment [was] done on friable asbestos material and [it] wasn't identified as a risk until the pile of rubbish was set fire to."

HMAS Adelaide is returning to Australia after volcanic ash crippled the warship's power.

In a statement, Defence confirmed safety precautions were immediately taken once the potentially hazardous material was discovered.

"The safety of Defence personnel is our highest priority and work on Atata Island ceased in the asbestos-affected areas after the discovery of the material," a Defence spokesperson said.

"The Australian Defence Force remains committed to supporting the Government of Tonga in their recovery efforts and are working with the government to identify other areas where asbestos may be present, whilst ensuring the safety of our personnel."

This week HMAS Adelaide's sister ship HMAS Canberra was formally welcomed to Tonga and is expected to remain there for several weeks completing further recovery efforts.

Australian soldiers have been clearing Atata Island as part of Operation Tonga Assist. (Defence Department: David Cox)