https://www.bbc.com/news/world-us-canada-54053811
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.
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 Dick, was given five years' probation and told to pay more than $8m (£6m) in damages.