Damage from the devastating wildfires in California exceeds $1bn (£760m) and is excepted to climb steeply, according to preliminary data.

"The preliminary insurance data for California wildfires losses is $1.045bn," state insurance commissioner, Dave Jones said. That valuation came from claims filed with the eight largest insurance companies in the area and the number does not include uninsured property.

Jones said the number would certainly rise, "probably dramatically so". Wildfires in the state destroyed almost 7,000 properties and killed 42, mostly elderly, people.

According to the Associated Press, the initial insurance total included 4,177 partial residential losses, 5,449 total residential losses, 35 rental and condominium losses, 601 commercial property losses, more than 3,000 vehicle losses, 150 farm or agricultural equipment losses, and 39 boats.

"In California we are seeing more severe and less predictable wildfires which poses enormous challenges to all Californians," Jones said at a press conference in Los Angeles.

State authorities say they have stopped the wildfires progressing but 15,000 people are still unable to return due to an evacuation order.

A Department of Forestry and Fire Protection spokesperson said that the number of destroyed buildings rose to 6,900 after authorities were able to reach more remote areas.

"The estimates are in structures and are mostly homes, but also includes commercial structures and outbuildings like barns and sheds," spokesperson Daniel Berland told the Associated Press.

Of the 38 people killed by the fires so far identified, 27 were over the age of 70. Many are thought to have been unable to escape the fast moving flames, the remains of some older couples were found huddled together.

Lawmakers from western states have introduced a bill that would provide $100m to help communities most at risk take preventative measures against wildfires. Washington's Senator Maria Cantwell said the effort would "create new tools to reduce fire risk and help better protect our communities".