The California Public Utilities Commission (CPUC) has opened a probe into whether infrastructure maintenance in Sonoma and Napa counties by Pacific Gas & Electric Corp. (PG&E) played a role in the wildfires.

Regulators ordered the San Francisco-based natural gas utility to “preserve all evidence” including equipment potentially related to the multiple fires, as well as internal communications regarding the disaster.

CPUC spokeswoman Terrie Prosper said the probe concerns PG&E’s activities in the area of the wildfires, “with specific focus on maintenance of facilities and vegetation management practices.” If the utility were suspected to have been involved, CPUC would follow up with “in-depth investigations.”

CPUC’s Elizaveta Malashenko, who directs the safety and enforcement division, in a letter to PG&E said, “All failed poles, conductors and associated equipment from each fire event” must be preserved, cataloged and tagged to allow regulators to review the evidence.

PG&E also was ordered to inform all employees and contractors to preserve “all electronic (including emails) and non-electronic documents related to potential causes of the fires, vegetation, maintenance and/or tree-trimming.”

Telecommunications companies also were ordered to preserve various evidence.

PG&E said it has been sharing information with the California Department of Forestry and Fire Protection (Cal Fire). In cases “where we have found instances of wires down, broken poles and impacted infrastructure, we have reported those to the commission and continued to share that information with Cal Fire,” a PG&E spokesperson said.

CPUC President Michael Picker said investigators have been working with Cal Fire inspectors to share findings as part of a memorandum of understanding signed in August.

“Cal Fire provides findings and immediate facts to us,” Picker said. CPUC then “follows after an event to conduct investigations if utility involvement is evidenced.”

PG&E said it has $800 million in insurance to cover potential losses, but warned that its financial condition could be materially affected if liabilities exceed coverage.

“Unless the narrative changes regarding the presumed root cause, it could be a long period of time before Cal Fire either exonerates PG&E or accuses them of being liable,” Evercore ISI analyst Greg Gordon said.

Cal Fire determined that the September 2015 Butte fire in Amador County was sparked by contact between a tree and a PG&E powerline. The fire, at the time the seventh most destructive in state history, burned for 22 days and spread into Calaveras County before it was fully contained.

Meanwhile, PG&E was making progress in restoring service to broad swaths of Northern California under siege from multiple wildfires.