A crude firebomb was discovered near the George Washington Parkway in Fairfax County yesterday morning, prompting police to close a two-mile stretch of the highway for 30 minutes while bomb disposal experts dismantled it.

The bomb, which apparently was constructed so that a smouldering cigarette would ignite its fuse, never detonated because the cigarette burned out before reaching the fuse, U.S. Park Police spokeswoman Sandra Alley said.

The bomb was disposed of by Army bomb disposal experts from Fort Lesley J. McNair, she said.

The bomb was located a foot off the roadway in a grassy median strip, the spokeswoman said.

It was discovered by a motorist stopped in traffic near the interesection of Belleview Boulevard and the parkway just outside Alexandria at about 6:45 a.m.

The motorist, whom police identified as Joseph E. Deely of Alexandria, called Park Police, who then closed off the parkway between Belle Haven Road and Morningside Lane and called in the bomb disposal unit. Deely declined to comment on the incident yesterday.

The bomb was dismantled without incident, and the light-to-moderate traffic, which had been rerouted, resumed along the parkway at about 7:30 a.m., the spokeswoman said.

The bomb consisted of an eight-inch glass jar filled with an inflammable liquid and "was definitely homemade," said Alley. "We sent it to the Alcohol, Tobacco and Firearms laboratory for analysis."

She declined to speculate on whether the bomb would have caused any damage had it detonated. "We won't know that until the contents are analyzed," Alley said.

No one has claimed responsibility for the bomb, she said.