WASHINGTON, D.C. -

Federal energy regulators are blaming inadequate planning and lack of grid coordination for the September 2011 blackout that affected millions of people in the Southwest and Mexico's Baja California.

The staff of the Federal Energy Regulatory Commission and North American Electric Reliability Corp. issued findings of their investigation Tuesday.

FERC Chairman Jon Wellinghoff says the report shows the growing need for more coordination of grid operations in the West.