Miami Mayor Carlos Alvarez said the U.S. Department of Homeland Security told him there "was no indication or evidence of foul play, not only in Dade or any other counties," Miami television station WFOR reported.
Florida Power & Light said its system worked properly when it cut electrical service to customers across South Florida, WBBH in Fort Myers reported. The utility said the problem began about 1 p.m. when a "disconnect switch" failed at a West Miami facility and then other equipment regulating power caught fire, the TV station said. Company officials said that triggered the system's designed response to cut power to preserve the rest of the grid.
"The system protected itself by going into rotating blackouts," Bob Trapp of the state's Public Service Commission told The Miami Herald. "It has a ripple effect throughout the state."
Two nuclear reactors at the utility's Turkey Point facility, as well as two oil-burning plants, tripped off unexpectedly, said Ken Clark of the Nuclear Regulatory Commission's regional office in Atlanta.
The state emergency operations center was partially activated, a state official said.