SEATTLE (USA TODAY) -- An American city tested itself for the first time Monday against a potential "dirty bomb" attack by terrorists, launching a full-scale drill to hone the skills of emergency workers and top decision-makers alike.

Clouds of acrid, black smoke, an explosion and a small, momentary fireball were the only immediately visible signs of the practice event staged about noon in an industrial area next to busy Interstate 5 south of downtown Seattle. One city bus lay overturned, another was damaged, and several cars were burned out. The debris was set up in advance to depict the immediate aftermath of a dirty bomb that the nation's homeland security officials believe terrorists might use to cause damage and sow fear in a large city.

Under the guidelines set up for the event, the attack that simulated the use of conventional explosives to release a cloud of radioactive material "killed" two people and "injured" 150, who were taken to nearby hospitals for decontamination and other treatment.

The drill and another exercise simulating a bioterrorism attack in Chicago are being staged this week as part of the federal government's effort to better prepare cities for terrorist attacks. The two drills, which cost $16 million to stage and 22 months to script, are so realistic that some of the bomb "victims" in Seattle screamed after seeing their graphic-looking "burns."

The Chicago attack involves a release of pneumonic plague. Hundreds of "victims" will begin reporting to local hospitals starting today, reporting flulike symptoms, to test the ability of the region's health care system to respond.

The federal government conducted terrorism attack drills in Portsmouth, N.H., and Denver in 2000, but this week's exercises are the first large-scale counterterrorism drills since the terrorist attacks of Sept. 11, 2001.

"Homeland security begins at home," Seattle Mayor Greg Nickels said. "When a disaster occurs, people do not call the White House, they call 911."

As the drill continues for the rest of the week, local, state and federal emergency teams will work through several scenarios they might someday confront in reality, including apprehending suspects.

"There will be a lot of lessons learned," Seattle Fire Chief G.P. Morris said.

One of the first tasks in a real dirty bomb attack is to assess the amount of the radiation contamination and sort out how many of the dead were killed by it. Experts generally believe that most deaths and serious injuries from such an explosion would be killed by the force of the blast and that the radiation effect would be minimal.

Much of the exercise involves teaching those on the front lines how to communicate with each other, resolve interagency conflicts and make decisions quickly. The issues being debated here:

* Determining how to keep the public informed during an attack and minimize panic.

* Coordinating communication so top officials such as the mayor and the governor can share information and ideas efficiently.

* Resolving conflicts that may arise when, for example, police and fire departments disagree over such things as the size of the perimeter surrounding the blast site, the number of streets to close, or how many officers are needed to guard the site.

* Assessing how decisions are made that may involve closing ports and airports or sealing border crossings.

* Balancing the need to preserve the crime scene against the need to care for victims.

Seattle Police Chief Gil Kerlikowske said the most mundane details could hamper the response during the first hours after an attack, and the drill provides an opportunity to resolve those now.

"How do the police first respond?" he said. "How do we make the hand-off to the FBI? In an evacuation, we're the primary department directing that. But what if there's not enough shelter space, or a clear direction on where to go?"

The drill was heavily publicized in advance with newspaper ads and letters to residents' homes.

Bob Kendall, an anti-war activist, dismissed the effort. "I think the government is purposely doing this to keep people in fear," he said.

But Dwight Jeppson, a banker from Bellingham, Wash, said he saw the benefit, despite the cost. "How can you do something like this without practice?" he said.

As the drill got underway in Seattle, Homeland Security Secretary Tom Ridge was in Washington, D.C., practicing his newly created department's role mounting the federal response to an attack. He attended a meeting of the Homeland Security Council, which included someone playing the role of President Bush.

The national alert status reached a simulated code red, the highest level. In a real-life situation, SWAT teams from the U.S. Park Police would be sent to protect national monuments and armored vehicles would surround the White House.

Some experts questioned the value of such scripted drills, but others said they're worthwhile.

The drills are "a good exercise," said Stephen Prior, director of the National Security Health Policy Center at the Potomac Institute for Policy Studies in Arlington, Va. "They will learn a lot." About the $16 million cost, he added, "It's money well spent."

At Seattle's Harborview Medical Center, where "victims" were put through decontamination tents Monday, Jeanne Cummings, an infectious disease control nurse, agreed. "Until you really do it, you don't get a sense of your strengths and weaknesses," she said.

Copyright 2003 USA TODAY, a division of Gannett Co. Inc.