SAN FRANCISCO (AP) — Pacific Gas & Electric says its equipment may have been involved in the start of a small wildfire that merged with the massive Dixie Fire now threatening homes in Northern California mountains.

PG&E says investigators are examining a tree found on power lines in Plumas County where the Fly Fire began July 22. The smaller blaze combined with the larger Dixie Fire two days later.

PG&E told regulators last month that the Dixie Fire may have been ignited July 14 when a tree fell on another one of its power lines.

PG&E equipment has been blamed for sparking some of the state’s deadliest wildfires.