The Fairview Fire in southern California is just 5% contained on Tuesday morning and has spread over 2,000 acres.
In an early morning briefing, Cal Fire Chief Josh Janssen said the fire started Monday afternoon in Fairview and rapidly expanded.
"This fire was moving in an opposite direction than it would normally do on a typical day this time of year," he said.
Multiple residential structures were burned. One civilian was injured in the blaze and two others were killed in Avery Canyon. Janssen said it was not known if the deceased were related or from the same household, but that they had been attempting to flee and were overcome by the wildfire.
The fire had aligned with the canyon for a "critical rate of spread."
CALIFORNIA WILDFIRE LEAVES 2 DEAD, EXPLODES TO 700 ACRES AS EVACUATIONS ARE ORDERED
Sgt. Brandi Swan, of the Riverside County Sheriff's Department, extended the department's condolences to the injured individual and to the family members of the two others.
She said that, as it was extremely hot in the burn zone, authorities had been unable to process the scene, but would later on Tuesday.
Schools in the Hemet Unified School District were closed as the wildfire remains a threat.
NORTHERN CALIFORNIA WILDFIRE EVACUATION ORDERS LIFTED AS NEARBY BLAZE GROWS
Multiple evacuation orders were issued on Monday and a warning was issued early Tuesday for Bautista Canyon Road.
Swan said the department was looking for vulnerable people who need assistance in evacuating.
Janssen told reporters that firefighters had been successful in obtaining the resources needed to provide suppression efforts on the fire and that they had worked continuously through the night.
However, unseasonably dry and drought-stricken fuel conditions had made matters more difficult.
He said there were a lot of factors to consider before the area could be ruled safe for homeowners, including preignition, power grid issues with potential charged lines and drought-stricken and fire-damaged trees.
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Triple-digit temperatures continue to blanket the state this year, with the heat wave putting major stress on the California power grid.
More than 25,000 were left without power on Tuesday morning, according to the tracker PowerOutage.US.
The Associated Press contributed to this report.