Mercer County was spared from the power outage that gripped much of the East Coast and parts of the Midwest on Thursday.

Pennsylvania Power Co., which serves all of the county, was able to react in time to prevent the grid meltdown from striking any of its territory.

"Locally, we switched most of our sources to internal power plants,'' said Randy Coleman, area manager for Penn Power. "We're fairly well isolated from the troubled grid. We shouldn't see any effects in Penn Power at all. Over the next three or four days things will be coming back to normal.''

A 90-minute power outage that hit 250 Penn Power customers in the Farrell area Thursday afternoon was blamed on a squirrel chewing on a fuse. The outage temporarily knocked radio station WPIC off the air.

Penn Power serves more than 155,000 customers in all of Mercer and Lawrence counties and sections of Allegheny, Beaver, Butler and Crawford counties.

At no point did Penn Power ask customers to curtail electricity usage, Coleman said.

FirstEnergy Corp., which owns Penn Power, said the company was dealing with widespread outages throughout its system in Ohio, including Youngstown, Cleveland, Akron, Canton and Toledo.

"Obviously, our priority is to remedy this,'' said Kristen Baird, a FirstEnergy spokeswoman.

The state Public Utility Commission reported that outages were experienced in Erie, Crawford, Warren, Venango and Clarion counties in the northwestern part of Pennsylvania. Brownouts or blackouts were also reported in Adams, Blair, Bradford, Cambria, Forest and Mercer counties, emergency management personnel said.

The outages were first reported at about 4:10 p.m., and some communities reported power returning as soon as two hours later. No major problems were reported in Pennsylvania.

"We have some rolling brownouts, but not anything of any magnitude," said Tom Lawson, the city of Erie's emergency management director. "For the most part, it's back on."

Much of Pennsylvania was unaffected; the lights remained on in Philadelphia and Pittsburgh. PJM Interconnection, the Valley Forge, Pa.-based company that manages the power grid in much of the Mid-Atlantic region, said it saw a massive outflow of power shortly after 4 p.m., but that its network quickly isolated itself, stopping the blackouts from spreading south.

The total number of people affected in Pennsylvania was not immediately clear, according to officials with the Pennsylvania Emergency Management Agency. Scott Surgeoner, a spokesman for FirstEnergy, said about 75,000 customers in Erie, Crawford and Warren counties were affected.

FirstEnergy and its subsidiaries have about 1.2 million customers in Pennsylvania.

"It's going to be a very slow, methodical process (getting power completely back to affected customers), more in the range of 12 to 18 hours for some, and possibly longer for others," Surgeoner said.

PEMA, however, suggested that affected regions would have power back by midnight.

Gov. Ed Rendell, at an outdoor check presentation in Erie when he learned of the outages, was remaining in Erie Thursday night and had canceled appointments to monitor the situation, spokeswoman Kate Philips said.

Erie police Lt. Robert Johns reported "widespread, but sporadic" outages. "It appears our major problem is probably traffic," he said. About 250,000 people live in and around Erie.

Control tower officials at Erie International Airport referred all questions to the Federal Aviation Administration, which said in a recorded message that all control towers had normal or generator power.

Power at the Hamot Medical Center in Erie went out about 4:25 p.m., activating hospital's generators, said spokeswoman Tina Andres.

"We are operating on emergency power and all of our critical care units are functional," Andres said. "We are in the process of turning all of the transformer switches over to the generators."

Andres said the hospital can function on generators for a week.

In Oil City, Police Chief Bob Wenner said officers were setting up traffic control points with street lights out.

"The streets are pretty well bare and people are heading home with a purpose," Wenner said. "We went through this just a few weeks ago with this storm and hopefully that will help us out."

The situation was a little more dire at Singer's Kreemy Deelite in Oil City, where Renee Grove said the business had five hours before its 32 gallons of ice cream melted. Generators were being brought in to try to save them.

"Actually we did eat some of it, because it is all going to melt," said Grove.

At Conneaut Lake Park in Crawford County, power was lost but no one was trapped on any rides, said a woman answering the phone at the amusement park.

Several flights scheduled to land in New York were rerouted to Pittsburgh and Philadelphia, while three flights from Pittsburgh International Airport to New York were canceled and flight delays were reported at Philadelphia International Airport.