Officials have blamed a gender reveal party for one of several wildfires raging in the US state of California.
A “smoke-generating pyrotechnic device” at the event sparked the El Dorado fire, which has now spread over 7,000 acres.
California is currently experiencing a record heatwave, with Los Angeles reporting its highest ever temperature of 49.4C (121F).
The National Weather Service described Sunday as “one of the hottest days since weather records began across much of south-western California”.
Last month, Death Valley National Park in California reported a temperature of 54.4C (130F) - what could be the highest temperature ever reliably recorded on Earth.
The largest blaze, known as the Creek Fire, has burned more than 73,000 acres and authorities said none of it has been contained.
It started at about 18:45 on Friday (01:45 GMT on Saturday) in the Sierra National Forest, an area of steep and rugged terrain.
Helicopters rescued more than 200 people trapped after the wildfire cut off the popular Mammoth Pool Reservoir, 40 miles (60km) north-east of Fresno. About 20 of them were hurt, with some suffering burns.
National forest spokesman Dan Tune said he did not know how close the fire was to the campsite, a popular boating and fishing destination.
The El Dorado fire meanwhile has spread over more than 7,000 acres.
The California Department of Forestry and Fire Protection, known as Cal Fire, blamed a “smoke generating pyrotechnic device, used during a gender reveal party” for the start of the blaze.
“Cal Fire reminds the public that with the dry conditions and critical fire weather, it doesn’t take much to start a wildfire”, the tweet read.
People who cause fires “can be held financially and criminally responsible”, it added.
California has seen nearly 1,000 wildfires since 15 August, often started by lightning strikes.
On Sunday, Governor Gavin Newsom declared a state of emergency in five Californian counties - Fresno, Madera, Mariposa, San Bernardino and San Diego - because of the wildfires.
Mandatory evacuation orders are now in place for a number of areas in Madera County.