Thousands of people working in downtown high-rise buildings left their jobs early Thursday to test the city's response to a terrorist attack or other emergency.

Participants, many with tennis shoes on their feet and water bottles in hand, left their offices and, under the direction of emergency teams, walked about five blocks to an assessment area. Once checked in, they were free to go.

Officials said more than 3,000 people took part in the voluntary drill, which involved four properties at the intersection of two main downtown thoroughfares, including the building that houses the Chicago Mercantile Exchange.

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The drill was staged in conjunction with the U.S. Department of Homeland Security's National Preparedness Month.

"As our country learned after Hurricane Katrina, an uncoordinated response can be deadlier than the disaster itself," said Harvey Camins, president of the Building Owners and Managers Association of Chicago, which represents 271 buildings and partnered with the city for the event.

All participants received surveys to give the city feedback.

"We want them to tell us what they thought went well, what didn't go so well, what they thought that they could do differently, and so we'll form a pretty substantial database," said Cortez Trotter, Chicago's chief emergency officer.

Celina Castillo, 30, who moved to Chicago from New York City two years ago, appreciated the drill because she was in New York during the Sept. 11 attacks.

"But in a real situation it won't be this smooth. There will be more chaos and confusion," Castillo said.

The exercise cost about $70,000, not including pay for police and other officials, said Cortez Trotter, Chicago's chief emergency officer. He said private companies paid most of that bill.

Some disagreed with the exercise. Betsy Ure, 22, and some friends handed out flyers that read, "FEAR can make you do all sorts of silly things."

"I think this is a scare tactic and unnecessary," Ure said. "Money would be better spent elsewhere."

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