BOULDER CREEK, Calif. (KRON) — Embers from the 2020 CZU Lightning Complex wildfire are still smoldering inside redwood trees with the potential to reignite new fires in the Santa Cruz mountains.

The deadly and devastating CZU wildfire was declared 100% contained by Cal Fire eight months ago, but multiple reignition fires have flared up within the burn zone this spring.

Firefighters hike half a mile to reach a reignition fire on May 1, 2021 in the CZU burn scar. (Photo by SLV Steve)

On Sunday, Cal Fire crews had to hike half a mile and lay down 5,000 feet of hose line to reach flames. The cause of the fire was traced to embers that surfaced from the roots of a redwood tree deep within Big Basin Redwoods State Park.

The blaze was contained to 6.5 acres.

Joanne Kerbavaz, a senior environmental scientist with California State Parks, told KRON4 that biologists are witnessing this natural phenomenon for the first time in their careers. Reignition fires in Big Basin were documented by historians in the early 1900s.

A fire engine navigates through thick forests on May 1, 2021. (Photo by SLV Steve)

“The embers can remain for months. It’s something that I had always heard about, how fire can linger. This is the first time I’ve experienced it. We have not personally seen this (before),” Kerbavaz said.

Winter rainstorms normally eliminate embers left over from major summer wildfires. But this past winter did not dump enough rain to get the job done.

Santa Cruz County entered “severe” drought status in April, according to the U.S. Drought Monitor.

Cal Fire plans to fly a plane with heat-detecting infrared technology to find embers in the CZU burn scar.

They want to find hot spots before wildfire season comes on full force with hotter, drier weather.

An air attack is used during an April 2021 wildfire in the Santa Cruz mountains. (Photo by SLV Steve)

The CZU fire perimeter stretched across 97% of Big Basin. The park remains closed due to dangerous conditions.

“Big Basin is compromised of many different types of vegetation. Some will rebound very quickly after the fire. In our lifetimes, we will still see beautiful forests in Big Basin,” Kerbavaz said.

Other hard-hit sections of beloved old growth forests will never look the same in our lifetimes, according to state parks officials.

Fire glows in the trunk of a tree during the 2020 CZU Lighting Complex. (Photo by SLV Steve)

“Redwoods grow very fast … up to 10 feet a year. They attain their height in 100 years. 100 years is a long time for us humans, but it’s a very short time in the life of a redwood tree,” Kerbavaz said.

Flames wrap around a tall tree during the 2020 CZU Lighting Complex. (Photo by SLV Steve)