Pacific Gas & Electric Co. warned investors Thursday it anticipates being held liable for at least $2.5 billion in damages for October’s Northern California wildfires — and could be on the hook for billions more. The San Francisco-based utility said $2.5 billion is the low end of its potential liability based on a growing number of lawsuits — now approaching 200 — filed against the company. PG&E executives did not set a ceiling for its exposure, stating there are too many unknowns to make a reasonable estimate. Insured losses from the fires are estimated to reach $10 billion, and some industry analysts have said the total could climb to as much as $15 billion. That far exceeds the approximately $840 million in insurance coverage PG&E listed in a financial filing Thursday. It also is significantly larger than the fines and settlement costs imposed on PG&E from the 2010 San Bruno natural gas pipeline explosion, which exceeded $1.9 billion.