Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) spent Monday training area police offices and sheriff's deputies on how to investigate post-blast crime scenes at a site near Lyons.

ATF agents set off several explosions, simulating improvised explosive devices (IEDs).

IEDs are not just found in terrorism investigations overseas, but even right here in Colorado. Investigators believe terror suspect Najibullah Zazi was practicing with chemicals to eventually make an IED.

Tuesday, the law enforcement officers will train on recovering evidence from the explosions.