What failed — and why?

Adeadly disaster on the scale of the Wine Country wildfires needs a probing examination. How it started is unclear, though wind-snapped power lines are a prime suspect. Also, as the flames took strength, a timely warning system proved spotty and ill-suited in alerting thousands to evacuate.

In each case, there must be a thorough review that can guide future precautions. Lives were lost, homes burned and businesses destroyed.

Sparking power lines knocked down by heavy winds are nothing new. Pacific Gas and Electric Co. acknowledges the blustery weather on Sunday night damaged its utility network in the areas where a string of fires started moments apart.

It will be up to the state Public Utilities Commission to take matters further. The utility is obliged to maintain its lines, free of vegetation that can shear wires and touch off wildfires. PG&E has paid hefty fines in the past for cutting back on maintenance that led to blazes.

It’s not just the utility, but the commission that needs to perform. Its oversight of PG&E was deplorably lax, as the 2010 San Bruno gas pipeline explosion demonstrated.

That disaster led to new leadership and orientation, at both the commission and PG&E, that face a test in determining if utility errors are responsible.

The warning system also needs a review. An areawide alert was held back out of fear it would lead too many people to clog roads. Other tactics targeted those in the fire’s path but failed to reach everyone. A more dependable and efficient system must be identified — and installed in short order.