TORONTO - Panic and mayhem swept across a Toronto college campus Saturday as about 100 screaming, blood-stained students hobbled in to receive medical care, but it was all part of a training exercise aimed at testing how emergency services might respond to a nuclear incident.

The mock disaster centered around a fictional "dirty bomb'' explosion and multi-vehicle crash on Hwy. 401 -- Canada's busiest highway -- in which a plume of radioactive dust was released into the air.

As part of the simulation, the students smeared fake blood on themselves and moved through Centennial College's make-believe hospital.

From the de-contamination area to the triage centre, the emergency room to the pharmacy, medical, paramedic and nursing students from several nearby colleges and universities as well as staff from the Rouge Valley Health System were put to the test.

"Gradually we're hoping we're building more and more capability within the health care system in Toronto and Ontario and in Canada to cope with mass casualty events,'' said Dr. Paul Arnold, an emergentologist with the University Health Network who was leading a group of government and health agency observers through the exercise.

"(Saturday's) exercise is particularly topical because everyone always worries about terrorist activities and bombs, but much of what we do today applies to building collapses, earthquakes, fires on subways and flu epidemics ... all of which are a lot more common than terrorist bombs.''

Among the participants were some 100 staffers from hospitals in Pickering and Ajax who were on hand to test their emergency preparedness plans. Event organizer Dr. Laurie Mazurik said while a dirty bomb situation is a little different than your typical nuclear disaster, the simulation is critical for these hospitals given their proximity to the Darlington and Pickering nuclear power plants.

"Although this isn't a nuclear exercise ... they have to be very well aware of a nuclear event and a release of radioactivity as well,'' she said.

"If something were to happen at a nuclear plant, they would be the ones that would be most affected by it.''

Noting the goal was really to see how staff cope at the emergency department and management levels, Arnold said the two levels were kept far apart from each other to make things even more difficult.

As is typical in a mass casualty event, the scenario also included the dissemination of false information which can lead to panic, patient overload, waiting room mob scenes and the breakdown of cell phone services.

"We want people to be functioning under stressful conditions ... so people will really be forced to think hard, make mistakes and recover from them. That process is what helps people learn,'' Arnold said.

From finding ways to get 20-30 more nurses on duty to figuring out how to deal with folks who are demanding medication they don't need, it's all part of the drill, he added.

The live, mass-casualty exercise caps a one-day conference examining the chemical, biological, radiation and nuclear readiness of Ontario hospitals and communities.

Mazurik said she's helped organize about 16 mass casualty simulations in four years, many of which have involved city paramedics, firefighters and police officers as well as federal and provincial government agencies.

A national exercise involving a pandemic is slated to take place next May, she said.

While the 9-11 attacks spawned the idea, Arnold said the 2003 outbreak of SARS in Toronto gave it a "sharper focus.''