A bomb threat to the Woodrow Wilson Bridge caused police to close the span for nearly 30 minutes during yesterday morning's rush hour, producing a massive traffic jam on the Capital Beltway.

Traffic was backed up several miles on the Virginia and Maryland sides of the bridge while police searched for a bomb between 8 and 8:15, according to Virginia State Police Capt. Robert L. Suthard. The bridge was closed later for 13 minutes more while police and police dogs concluded the search at 9:30, failing to find any explosive.

The traffic jam was exacerbated by construction on the bridge, Suthard said. Work crews who are redecking the mile-long bridge are supposed to work at night and clear the span by 6 a.m.

But work planned near the Virginia side of the bridge Monday night took longer than expected and construction workers were still at work and some of the bridge's six lanes closed when police arrived shortly after a male voice warned Virginia police of a possible bomb.

"You hate like hell to have to close the bridge because of the inconvenience to everybody . . . , but we didn't have any choice," Suthard said. "It's a precaution we have to take even though almost all bomb threats are hoaxes."

He said a male voice called the Northern Virgina State Police office about 7:40 a.m. and said "You better stop traffic on Woodrow Wilson Bridge. Dynamite on bridge. It will blow at 8 a.m.," and then repeated the message a second time, Suthard said.

Maryland State Police were called and a joint decision to close down the bridge was made, said Suthard.