GRANDFATHER MOUNTAIN, N.C., SEPT. 11 -- The final link in the Blue Ridge Parkway, delayed 20 years by political and environmental battles, was opened here today but not before a bomb threat briefly delayed events.

National Park Service police said the bomb scare was directed at the Linn Cove viaduct, the most environmentally sensitive portion of the final 7 1/2-mile section of the mountaintop road that winds through Virginia and North Carolina.

No explosive device was found, authorities said.

Park Service rangers blocked off the 1,243-foot viaduct, the most spectacular of the dozen bridges that help fill the last link in the scenic route, dedicated 52 years ago today as a make-work project of the Great Depression.

Officials from North Carolina and Virginia participated at the ribbon-cutting, and Transportation Secretary Elizabeth Hanford Dole spoke at another ceremony this afternoon.

Several scheduled speakers, including North Carolina Gov. James G. Martin (R), could not attend because a light drizzle and low clouds prevented their helicopters from landing in the nearby meadow, whose elevation is 5,837 feet.

Among those who made it was A.L. Philpott, speaker of the Virginia House of Delegates, who chided North Carolina officials for taking so long to finish their portion and then gaining publicity for finally doing it.

Philpott noted that construction of the parkway and its companion Skyline Drive to the north had begun in the administration of President Franklin D. Roosevelt and was considered "a hallmark" of the career of the late Sen. Harry F. Byrd Sr. (D-Va.). Philpott said Byrd "was never known to be a supporter of liberal causes or a spendthrift."

The Florida engineering firm that designed the viaduct said the $10 million bridge, which snakes around a boulder-strewn cove in a sweeping "S" curve, is the most complicated segmental concrete bridge ever built.

Nearly all of the new section is elevated, or bridged, to eliminate massive cuts and fills opposed by environmentalists. The only trees cut along its path were beneath the superstructure.

Opening of the final segment, with its 45 mph speed limit, ends a tortuous 14-mile detour and will allow motorists to make a leisurely and uninterrupted 470-mile trip from Rockfish Gap, at its link with the Skyline Drive near Waynesboro, Va., to Oconaluftee outside Cherokee, N.C.