An arsonist has set fire to Cedar Rapids Jefferson High School for the second time in two weeks. Firefighters responded to an alarm at the school around 12:15 this morning. Crews found the window of a portable classroom had been broken, and a small fire had been set. The fire damaged an air conditioner and some carpet before burning itself out. Last week, an intentional fire at Jefferson damaged an office area inside the school. Investigators say that fire began when someone broke in and ignited some books. Both fires remain under investigation.