Iowa City police and fire investigators have teamed up to investigate a string of fires. City Fire Marshal Roger Jensen says all have broken out between one and four in the morning, and all six happened since April 20. Two were of no consequence, caused no property damage but were set and went out, as they determined after property owners noticed and called the investigators who say they were similar to the other fires. Jensen says they look like crimes committed on the spur of the moment, with materials found at hand…often dry leaves and debris in the industrial area where all the fires have occurred.One was a construction site where sheets of plywood were arranged like a chimney that made a fast-burning site for the fires. In all but one case the fires were set on the outside of the building with combustible materials that were already there, and he recommends business owners look around the property and consider what’s “burnable” on the outside of their building. Clearing it away might stop an arsonist who acts on impulse, the fire marshal says. Jensen didn’t want to speculate on who might be setting fires on the city’s north side. Jensen says it does appear that “there are criminal elements present,” and there could be serious consequences for the perpetrator. The latest fire Tuesday morning did 30-thousand dollars damage to a business called Auto Trim, and one earlier at a lumberyard destroyed equipment and a truck, for a total of what the owner says was a 100-thousand dollar loss.