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.
Gender reveal parties are celebrations announcing whether expecting parents are going to have a girl or a boy. In recent years, several large-scale parties have gone wrong, even resulting in the death of a woman in 2019.
"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.
This is not the first time such an event has started a wildfire. In April 2017, a gender reveal party in Arizona sparked a week-long wildfire which burned through 45,000 acres.
The father, Dennis Dickey, was given five years' probation and asked to pay damages.
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.
Authorities in Los Angeles county have also closed a number of hiking trails in the Santa Monica mountains due to the soaring heat.
Malibu Search and Rescue urged people not to hike in the temperatures, after one hiker died:
Effective immediately, we have been advised that all trails in the #SantaMonicaMountains will be closed through #LaborDay. We responded to several heat related rescues today, including one hiker who unfortunately perished. PLEASE DO NOT #HIKE IN THIS #HEATWAVE. #CAwx #LAHeat pic.twitter.com/B1ZdOu46S3— Malibu Search Rescue (@MalibuSAR) September 6, 2020