California fire investigators appear to be investigating what role, if any, a prestigious Napa Valley winery played in the start of the almost 7,000-acre Pickett fire, which is still threatening hundreds of buildings and dozens of wineries.

A spokesperson for Hundred Acre, a popular Calistoga-based winery, confirmed Friday that company representatives had recently spoken with fire investigators who are trying to figure out what started the region’s largest fire this year.

“They are working cooperatively with the investigation into the Pickett fire,” said Sam Singer, a spokesperson for One True Vine, a company that includes Hundred Acre wines. The San Francisco Chronicle has described Hundred Acre as a “cult Cabernet” winemaker.

While the cause of the fire remains under investigation, a source with knowledge of the discussions at Hundred Acre told The Times that the investigators were looking into the possibility that discarded ashes from the vineyard had sparked the major fire.

The Pickett fire ignited Aug. 21 at 2343 Pickett Road just outside of Calistoga, according to the California Department of Forestry and Fire Protection. That address is part of the Hundred Acre property, Singer confirmed.

Singer declined to comment on reports about the discarded ashes. However, he made clear that there was no controlled burn on the property that might have gotten out of control.

Officials with Cal Fire, which is leading the fire investigation and response, did not immediately respond to a request for comment.

The Pickett fire remained at just under 7,000 acres as of Thursday, with 33% containment, according to Cal Fire reports. It broke out amid a major heat wave, prompting evacuation orders and warnings, including many that remain in place.

The blaze has not grown in several days, but Cal Fire reported Thursday that “large fuels continue to smolder within the fire perimeter as firefighters work to construct control lines within steep, rugged terrain.”

While the extent of damage to vineyards and properties around the region hasn’t yet been assessed, no structures have been reported destroyed or damaged. Singer said Hundred Acre’s properties have had road and infrastructure damage, but no buildings or vineyards were affected.

There are more than 2,500 people assigned to the fire response, according to Cal Fire.