California's iconic Joshua trees in the Mojave National Preserve have been severely damaged by a wildfire that has been burning since last week, officials said.

The York Fire has been mostly contained as of Friday, but several trees were burned. Officials from CalFire and the National Park Service told reporters earlier in the week that they will not know how many trees have been destroyed until it is safe enough to survey the area.

The fire began on July 28 and has been burning through the Mojave National Preserve, according to fire officials. The cause of the York fire is still under investigation.

Over 400 firefighters were deployed to fight the blaze and were assisted by experts in wildlife biology, plant ecology, archaeology, and geology "to minimize the impacts of wildfire of suppression activities," CalFire said.

Crews carved fire lines without the use of bulldozers to reduce the impact in the ecologically-sensitive region, fire officials said.

Rain from earlier in the week helped firefighters.

As of Friday morning, firefighters were able to contain 85% of the blaze, which has affected over 100,000 acres in the California and Nevada wildlands, CalFire said.