What caused the Thomas Fire? A year later there's no official answer

One year after the Thomas Fire began in Ventura County, eventually becoming one of the largest wildfires in the history of California, officials have yet to release a cause.

A home  burns in the Thomas Fire in Ventura in the early morning hours of Dec. 5, 2017.

Ventura County Fire Chief Mark Lorenzen, whose agency has led the investigation into the incident, said last week a report is close to being unveiled.

"We're hopeful that we should have the cause and the whole investigation report available within a few weeks," he said Wednesday.

The chief said he met with arson investigators Wednesday, and they were flying to Sacramento Friday to discuss the findings with the California Department of Forestry and Fire Protection.

Before it was fully contained on Jan. 12, the Thomas Fire would consume 281,893 acres, destroy 1,063 structures, damage 280 more and result in the deaths of a Santa Paula woman and a Cal Fire engineer from San Diego. 

For a time, the Thomas Fire was the largest wildfire in state history although it was eventually surpassed in the summer of 2018 by the Mendocino Complex Fire, which eventually burned 459,123 acres. The Thomas Fire now stands as California's second largest fire.

In related news:

Due to the destructive and historic nature of the Thomas Fire, the release of the cause has been highly anticipated. Lorenzen said Ventura County Fire has received a large number of public records requests for the report.

"We haven't been able to share any information as of yet because it hasn't been available," the chief said. 

Tuesday marks the first anniversary of the fire's ignition points in the hills near Santa Paula, and Lorenzen acknowledged the length of time that has elapsed since the fire began, with no cause yet determined.

More:Ventura psychiatric hospital damaged in Thomas Fire reopens

"It's a challenge sometimes with the complexities of the fire," he said.

"Sometimes you have some challenges with winds and having it start in a remote area. That's really, I think, what caused it," he said regarding the length of the investigation.

Pushed by Santa Ana winds and fed by dry vegetation and single-digit humidity, the fire exploded in size after it began on the evening of Dec. 4, reaching the city of Ventura within hours after it started.

Wind speeds of about 60 miles per hour were experienced on the night fire began, according to reports from the National Weather Service.

"The investigation began almost right away," Lorenzen said. "In our initial brush fire response, we typically will respond with a cause investigator."

In the following days and weeks, the fire would tear its way through Ventura County and into neighboring Santa Barbara County, displacing thousands of residents.

Lorenzen said investigators with Ventura County Fire, the Ventura County Sheriff's Office and the California Department of Forestry and Fire Protection were cautious at every step due to intricacies of the incident.

"Because it was such a big fire and there was so much liability and responsibility attached to that, they wanted to make sure everything was absolutely in order before they released it," he said.

More:Ventura Botanical Gardens welcomes visitors back after Thomas Fire devastation

The chief said investigators recognized the scale of the damage and destruction, and as they always do, they wanted to make sure they got it right.

"This was just bigger and more complicated than most," he said.

Lorenzen said a team of investigators was assigned to the incident full time although the chief did not have an exact number of members.

In the wake of the fire, and the subsequent mudslides in Montecito that killed 21 people, numerous lawsuits were filed against Southern California Edison, alleging that its equipment contributed to the blaze.

On Oct. 30, the utility company said in a release that its equipment was associated with an ignition point near Koenigstein Road in Santa Paula.

"The lawsuits really weren't relevant to the investigators as they were doing it," Lorenzen said.

More:Here's a comprehensive list of our original Thomas Fire coverage