US troops raided a car bomb factory west of Baghdad with five buildings full of propane tanks and ordinary chemicals the military believes were to be used in bombs, a spokesman said Thursday, a day after insurgents blew up a truck carrying chlorine gas canisters. Maj. Gen. William Caldwell said the chlorine attack Wednesday - the second such "dirty" chemical attack in two days - signaled a change in insurgent tactics, and the military was fighting back with targeted raids. "What we are seeing is a change in the tactics, but their strategy has not changed. And that's to create high-profile attacks to instill fear and division amongst the Iraqi people," he told CNN. "It's a real crude attempt to raise the terror level by taking and mixing ordinary chemicals with explosive devices, trying to instill that fear within the Iraqi people."