Investigators have determined an improperly installed electric livestock fence sparked the County fire, the largest blaze currently burning in California, Cal Fire said Wednesday.

The County fire, which has consumed 90,288 acres in Yolo and Napa counties, was 86 percent contained Wednesday morning, Cal Fire said.

The fire started June 30 on Highway 16 in Yolo County’s rural community of Guinda. Winds pushed it south, burning down into Napa County near Lake Berryessa.

The flames have destroyed 20 structures and damaged three.

Cal Fire spokesman Will Powers wasn’t able to provide specifics about the cause and what led investigators to conclude the electric fence sparked the blaze. He also did not provide details on where the fence was located, who installed it and what was wrong with the installation. He said information would be released as they become available in coming weeks.

The responsible party has been cited, Cal Fire said. Consequences for that citation could include unspecified criminal charges or responsibility for the cost of fire suppression efforts or property damage, Cal Fire Deputy Chief Scott McLean said. Specific determinations will be up to the district attorney’s office, he said.

The Yolo County District Attorney’s Office Wednesday afternoon received the incident report, Chief Deputy District Attorney Jonathan Raven said. He said he could not release the investigative file amid the ongoing case, citing public records laws.

However, Powers did not provide information on who was responsible or the repercussions of that citation or associated penalties.

Containment in the blaze burning east of Lake Berryessa increased 3 percent overnight, and it’s expected to be fully contained Thursday, Cal Fire said.

Crews were attacking “islands” of fire inside the northern portion of the blaze, Cal Fire Battalion Chief Josh Janssen said. They also were mopping up hot spots and creating a larger buffer zone, he said.

The weather is expected to reach triple digits with low humidity Wednesday, which could pose a challenge for crews navigating the steep and rugged terrain, he said.

“We’re confident we’ll be able to close this fire out in the next few days and be ready for the next one,” he said.

Meanwhile, Lake County residents already shaken by the now 100-percent contained Pawnee fire were rattled by another 80-acre fire that broke out Monday afternoon near Spring Valley Road and New Long Valley Road.

The blaze was 90 percent contained Wednesday morning, Powers said. No advisory or mandatory evacuations were ordered in the area, he said.

The blaze burned into the Pawnee fire scar, Janssen said.

Check back for updates.

You can reach Staff Writer Hannah Beausang at 707-521-5214 or hannah.beausang@pressdemocrat.com. On Twitter @hannahbeausang.