Damage caused by the Tonga volcanic eruption and tsunami two weeks ago is still being assessed by insurers, with clean-up efforts at the Pacific Island hampered by thick layers of ash and communications difficulties.

The Hunga Tonga-Hunga Ha’apai underwater volcano erupted about 65km north of Tonga’s capital Nuku’alofa, causing a cloud of ash and triggering a tsunami on January 15.

Risk Frontiers says eyewitnesses reported a plume of ash about 5km wide, rising 20 km into the atmosphere, while the initial eruption could be heard as “loud thunder sounds” in Fiji, more than 800km away.

Tsunami warnings and advisories were issued for Tonga, America Samoa, Fiji, Vanuatu, New Zealand, the US, Canada, Japan, Chile and Australia.

New Zealand insurer Tower said after the event that it had 2500 customers in Tonga and its local branch was open and assisting policyholders.

Loss adjusters Crawford & Company said it had enacted a catastrophe plan following the eruption and tsunami.

“The scale of the devastation is expected to be extensive and a significant clean-up will be necessary as many businesses and homes have been completely destroyed,” it said in a January 19 market update.

Far-flung impacts included wave damage to the Tutukaka marina on New Zealand’s North Island, with some boats submerged and other vessels and infrastructure damaged.

The Insurance Council of New Zealand says the cost of damage at the marina is likely to run into the millions of dollars, with preliminary claims data still being collected. Final figures are likely in late March.

The tsunami also reportedly caused an oil spill in Peru as a ship unloading crude supplies to a refinery was rocked by large waves.