Hundreds of Washington residents took cover in buildings, raced to outdoor balconies and made panicked calls to local police and fire departments Saturday night, unaware that the loud explosions they heard were from a fireworks display near the John F. Kennedy Center for the Performing Arts.

The noise, which sounded like machine-gun fire to some and like bombs or cannonballs to others, could be heard as far away as upper Northwest Washington and Falls Church.

D.C. fire department dispatchers were deluged with calls from worried residents for more than an hour, spokesman Alan Etter said. "They couldn't count the number of calls," Etter said. "They were swamped."

District emergency officials, aware of the scheduled fireworks display, nonetheless sent out firetrucks as a precaution in response to the numerous reports of noise, smoke and haze, Etter said.

The seven-minute show, which launched the Kennedy Center's month-long Festival of China, was the creation of pyrotechnics designer Cai Guo-Qiang, who had referred to it as an "explosion event."

But in a region all too familiar with color-coded terror alerts -- and not used to hearing fireworks on days other than the Fourth of July -- the loud, unexplained noises in the nighttime sky sowed fears of something far more ominous.

"It sounded like a kind of rocket or something," said David Zhang, 35, a consultant who was a half-block from his apartment in Foggy Bottom when he first heard the bangs and booms. Like many others interviewed yesterday, he said the explosions did not sound like typical fireworks. "I've never heard fireworks this loud. They just didn't sound right," Zhang said.

Alicia Adams, the festival's curator, said Kennedy Center officials had pushed for publicity about the fireworks show because they were eager to promote the work of Cai, an international artist who also has staged fireworks in London and Australia. She said local news media had run stories about the show in the preceding days.

"We are certainly sorry that people had that experience," said Adams, vice president for international programming at the Kennedy Center. "For the people who were here and read about it, it was on the banks of the Potomac, and it was a wonderful celebration."

The display began around 9:50p.m., said Kennedy Center spokeswoman Tiki Davies. The shells were launched from nine small boats and one barge in the Potomac River, to heights of 80 to 150 feet. For the finale, spectators saw what festival organizers called a "tornado" -- a thick, funnel-shaped, white plume of smoke suspended 500 feet in the air.

Daniel Ostick, 35, heard the noise from his fourth-floor condo at Columbia Road and 16th Street NW in Adams Morgan.

"When fireworks are happening in Rosslyn or the Mall, I can see them out my window," he said. "I had no idea what it was. It sounded like a series of explosions."

In Arlington, Sheila Cordaro, 34, a stay-at-home mother who lives about a mile from the Ballston Metro stop, said she feared an accident on the tracks.

"It sounded like something had been hit and dragged across the tracks for 10 seconds. It happened again one minute later and then again," Cordaro said.

The blasts could even be heard during a student play at Sidwell Friends School in the 3800 block of Wisconsin Avenue NW.

"Constituents were calling me to ask me if it was a terrorist attack," said D.C. Council member Jim Graham (D-Ward 1). "You don't expect to hear a major fireworks display in October."

Outside Zhang's building in the 2100 block of L Street NW, residents rushed to their balconies to locate the source of the noise but were too far away to see the pyrotechnics. In that same area, pedestrians ran inside buildings in fear.

Brooke Taylor, a 19-year-old George Washington University freshman, heard the disturbance from her dorm room at Fulbright Hall, in the 2200 block of H Street.

"Everyone in the dorms rushed to the halls to see what was going on," Taylor said. "We then went to the roof and saw gray smoke with a reddish taint. Someone was, like, 'Is that a nuke?' People were saying, 'Which way is the Pentagon?'"

Arlington resident Jim Pebley was online yesterday, reading his neighbors' complaints and comments. In the age of terrorism, he said, residents simply could not dismiss the sounds.

"I think everyone's a little jumpy right now, don't you?" Pebley said.

Staff writer Nikita Stewart contributed to this report.

A fireworks display at the Kennedy Center frightened residents.