Fla. Power Outage Affects Millions

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Raw Video: Power Outages Across Florida

Widespread power outages are being reported around southern Florida, including parts of Miami. The state's largest power company, Florida Power and Light, is investigating the cause.

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Laura Keehner, a spokeswoman for the Department of Homeland Security in Washington, said there was "no indication of a terror nexus at this time."

Olivera apologized to customers and state officials Tuesday evening. By 5 p.m., he said, 8,000 of the 475,000 households and businesses affected in the FPL system were still without power.

He said that a faulty disconnect switch at a substation in west Miami-Dade County had failed and that a piece of equipment controlling voltage at the substation caught fire.

Small incidents can sometimes lead to widespread power failures because they may create a cascade of secondary problems. When demand for power suddenly exceeds the electrical supply, transmission and distribution systems begin to cut off customers.

Power companies call these automatic shut-offs "shedding the load," and they are meant to prevent further damage to the power grid.

Tuesday's fire led to problems in two major power lines between Miami and Daytona and the shutdown of 20 other substations. "Under normal circumstances, an equipment failure of that kind would not cause the extended outage we saw today," Olivera said.

At 1:09 p.m., about a minute after the substation problem, the two nuclear reactors at FPL's Turkey Point Plant detected "a disturbance in the grid" and shut down, as they are designed to do. That took 1,400 megawatts of generating capacity offline. Two coal-fired units at the same complex also shut down.

Olivera said that the company's nuclear units had "shut down as designed."

Within three minutes or so of the substation problem, customers began to lose power. Because other Florida utilities are connected to the same grid, FPL's problems spread throughout the state.

Olivera estimated that, at the peak of the outage, a million households and businesses were affected.

A Progress Energy spokesman, Scott Sutton, said 153,000 of its customers were affected.

The outage was not nearly as extensive or prolonged as the regional blackout on Aug. 14, 2003, the largest in North American history, when tree branches damaging power lines in Ohio ended up causing power loss to 50 million people in eight states and Ontario, Canada.

But the disruption Tuesday was significant enough that the Florida state emergency operations center in Tallahassee was monitoring the situation. Officials said they were ready to provide assistance if the outage persisted after dark and local governments needed help to maintain order.

By sundown, however, order and electricity had been restored to most of the affected areas. Authorities said an investigation could take weeks.

Mufson reported from Washington.