The accidental release of pepper spray in a downtown office building yesterday sickened dozens of people and triggered a massive response by authorities worried about a terrorist attack or chemical spill.

Scores of firefighters and police officers responded to the lunch-hour scare in the 1900 block of I Street NW, just blocks from the World Bank and headquarters of the International Monetary Fund.

Both financial institutions were mentioned as potential terror targets last month by homeland security officials. Word of the incident sent the stock market into a brief 70-point plunge after fire officials said they were treating the scare as a potential "mass casualty" event.

About 1,500 people evacuated the building, which has restaurants and shops and covers much of the block between I and K streets NW. Dozens were briefly quarantined in a nearby park to be assessed by medical crews, and police closed streets in the surrounding blocks for about two hours.

Firefighters specializing in hazardous materials set up a decontamination and triage area in the middle of an intersection. One person, who suffered from asthma, was taken to a city hospital for treatment. Four others were treated at the scene with oxygen, fire officials said.

Several victims had their eyes flushed, and about 130 people complained of difficulty breathing, burning eyes and other symptoms associated with being exposed to mace or pepper spray, the officials said.

They said the incident began in a restaurant about 12:30 p.m. when a boy grabbed a chain around a girl's neck that contained a small canister of pepper spray. He touched a button on the container, discharging the spray near an air-intake vent, police officials said.

Officers questioned the youths and witnesses yesterday. Police officials said they did not expect to file charges. Police said the teenagers are students at School Without Walls, a high-performing magnet school in the 2100 block of G Street NW. The students might have been taking their lunch break at the time of the incident, police said.

Workers in the building, which houses a variety of businesses and government offices, described starting to feel sick while they were sitting at their desks or lunch tables.

Clarance Fletcher, an employee at the U.S. Department of Transportation, said he was at his desk on the fifth floor when he began to cough.

"It was like this burning sensation," Fletcher said.

Some said their first thoughts were of terrorism, especially in light of heightened warnings and stepped-up patrols at the World Bank and IMF.

The large response was criticized by several people at the scene who said authorities acted swiftly but seemed unorganized. Some victims were never quarantined, they said, adding that officers gave conflicting orders on the street.

Jon Poling, a 27-year-old lawyer grabbing lunch in the building with a friend, said he began coughing and noticed that others were also coughing uncontrollably. He couldn't smell anything, and that frightened him, he said.

After the evacuation, police gave different orders and did not set up a quarantine area quickly enough, allowing some of those exposed to wander away from the area, Poling said.

"It's a shame we're not ready" for a terror attack, Poling said.

Others said firefighters and police overreacted and were not cautious in their statements to the media. They also said the media might have played a role in fueling fear about the incident.

Andy Brooks, a vice president in charge of equity trading at T. Rowe Price in Baltimore, said the comments bordered on "reckless" and helped spark the stock market dive.

"The market got wind of something that looked like a mass casualty event and the market sold off rather dramatically," Brooks said. "It's really evidence of how nervous the market is about terrorism. People who sold on that information really got clobbered. It reminds us of the importance of having information verified."

D.C. police and firefighters deflected the criticism, saying they did a solid job of containing the incident on a busy block and have to take every such response seriously, especially in a city that is a tempting target for terrorists.

"I think the response was great," said D.C. Police Chief Charles H. Ramsey. "We can't just parachute in."

Battalion Chief Larry Schultz, head of the fire department's special operations division, said firefighters and police did the best they could when they arrived and found hundreds of people emptying onto the street and complaining of difficulty breathing.

A hazmat crew sets up a decontamination area outside the Baja Fresh restaurant at 1990 K St. NW.Mike Ambrose waits with others at a park. He was at Washington Sports Club when the evacuation began. Dozens were briefly quarantined at Edward R. Murrow Park to be assessed.