The US Insurance Information Institute (III) says it is too early to assess the damage bill from tornadoes that hit the states of Kansas, Kentucky, Missouri, Indiana, Illinois and Tennessee last week.

The death toll has risen to 40 and is expected to climb as rescuers search through the remains of many flattened buildings. More than 300 people have been injured.  

Residential claims may be low as many homeowners did not have mortgages and were not required to have insurance.

Despite this, the III says the industry has responded quickly to the disaster.

Experts have been surprised by the severity of the storms this early in the year. It follows on from a deadly season last year with 1725 tornadoes killing 593 people.

According to the III, US tornadoes have caused $US97.8 billion ($91.1 billion) of losses between 1990 and 2009.

It makes these weather events – second only to hurricanes which cost $US152.4 billion ($142 billion) during the same period – the costliest natural disasters.