The bridge that carries Rte. 301 across the Potomac River from Charles County, Md., to King George County, Va., was closed yesterday after structural damage was discovered. Officials said repairs may take "a couple of days."

Motorists were directed to use the Woodrow Wilson Bridge on the Capital Beltway as an alternate crossing. Some were turned back at the bridgehead in Maryland yesterday and directed north to the Beltway, police said.

The 39-year-old Gov. Harry W. Nice Memorial Bridge was shut down at 5 p.m. after inspectors making an annual checkup found concrete was flaking on one of the approximately 80 piers that support the two-mile-long span.

"We shut it down for safety until we can get into it and find out what is the problem," said J. Leon Pilkerton, the superintendant of the toll crossing used last year by 2.6 million vehicles.

"Our department felt it was better to shut it down than take a chance," Pilkerton said of the bridge, which is operated by the toll facilities administration of the Maryland Department of Transportation.

He said the cause of the flaking, or "spalling" as it is described, was not known. but it was speculated that it may have been due to the effects of ice. The pier in question is near the Virginia side of the bridge and its top is about three or four feet above the water level.

Temporary repairs will be started as soon as possible, Pilkerton said, and would consume "hopefully only a couple of days."

Pilkerton said the Rte. 301 bridge once was a key segment of the main highway route from the Northeast to Florida, supplanted only by the opening of Rte. I-95.