The damage bill to insurers from Hurricane Irene, which devastated the east coast of the US in August, has surged 18% to $US4.3 billion ($4.42 billion).

However, the insurance losses are likely to keep rising after the deadline for filing a “proof of loss” claim was extended by two months to January 23 in 15 states.

Estimates made in September predicted the insurance bill will top $7 billion ($7.2 billion).

The revised loss estimates were revealed by a survey of insurance companies conducted by the Property Claim Services (PCS) unit of the Insurance Services Offices.

They do not include the cost of the flood damage insured by the National Flood Insurance Program. Flooding was worse in some places than the storm damage.

Damage from Hurricane Irene has so far triggered more than 855,000 insurance claims, with individual claims worth an average $5000, according to the PCS.

The worst damage was done in New Jersey in the northeast, where claims have reached $915 million ($940.48 million) and North Carolina where they stand at $900 million ($925 million), the PCS said.

Fourteen states have sustained at least $10 million ($10.27 million) in damage claims and a further eight states more than $100 million ($102.77 million).