Flames have scorched nearly 15,000 acres since the fire broke out Saturday.
It's now up to eight percent contained as of Monday morning.
About 1,200 campers at the Hungry Valley Park State Vehicular Recreation Area were ordered to evacuate Saturday night, and authorities closed Pyramid Lake, which was expecting thousands of visitors for Father's Day, due to the threat of the Post Fire, CAL FIRE said.
Two adults and a child were injured, but their conditions have not been released.
In a social media post, Kings County Firefighters announced Sunday they were heading to help battle the Post Fire.
The cause of the fire is still under investigation.