FORT INDIANTOWN GAP - David Marx, a University of Scranton chemistry professor, was pretending to be a terrorist.

In his lab at the drug-raid house run by the Northeast Counterdrug Training Center at Fort Indiantown Gap, Marx and his fellow terrorist posers were pretending to concoct a deadly powder of abrin, enough to kill 2,500 people. SWAT teams, hazardous-materials teams, police and firefighters were trying to stop them.

It was part of an eight-county counterterrorism exercise involving nearly 3,000 people at three military installations and 16 hospitals organized by the South Central Pennsylvania Regional Counter-Terrorism Task Force.

The exercise was the largest of its kind in south-central Pennsylvania, according to spokeswoman Bernadette Lauer. Emergency personnel from Dauphin, Lebanon, York, Perry and Cumberland counties were among the participants.

As part of the scenario, dignitaries and visitors at two other installations -- the Letterkenny Army Depot in Franklin County and the Defense Distribution Center in York County -- were said to be attacked with abrin, a poison made from the seeds of the rosary pea plant. "Victims" were taken to hospitals, where medical personnel tended to them.

There is no antidote to abrin, Marx said. Medical personnel can help only with the symptoms.

At Fort Indiantown Gap, the exercise started early yesterday morning when emergency personnel were told of possible terrorist activity.

When SWAT teams from Lebanon, Dauphin, Lancaster and York counties broke into the house, they found a lab set up with directions for making abrin posted on the wall. The word "death" was written on the page in Arabic.

The terrorists simulated shooting, and the teams pretended to return fire. After the terrorists were taken into custody, the SWAT teams went outside to be decontaminated, and the hazardous-materials teams went inside to shut down the lab.

The idea is "to get all these agencies working together," said Sgt. Richard Breach, a spokesman for the Northeast Counterdrug Training Center, which is run by the Pennsylvania National Guard.

The high-tech raid house used in the exercise has 104 cameras mounted inside so participants can evaluate their responses. A control room lets organizers add sounds, sights and smells to the scenario, fill rooms with smoke or program robotic enemies to pop out and start shooting.

A virtual reality room acts like a PlayStation, "but to the millionth power," said facility manager Sgt. 1st Class Shane Carlin.

The house was built to teach law enforcers to raid drug houses, but in the last few years, it has been used for counterterrorism training, Breach said. Counterterrorism classes increased from one in 2003 to 78 this year, Breach said. Drug- and bomb-sniffing dogs train there. Classes are free to first-responders, such as fire department and ambulance personnel.

The training center got $3.58 million this year from the Department of Defense, according to U.S. Sen. Rick Santorum's office.

David Gingrich, team commander for the Lebanon Emergency Services Unit, a SWAT team, said the counterterrorism training yesterday was invaluable.

"The rules of the game are completely different," he said. "They don't care about life or limb. Negotiations don't help. The dynamics are completely different, and that's why we have to train for it."