After a suspicious car fire triggered a 2½-month arson investigation, Longmont police finally fingered a squirrelly suspect. They decided a squirrel seeking a cozy home had built a paper-filled nest in a cranny of the car engine and the paper ignited when the engine got hot, Longmont police Cmdr. Jeff Satur said Tuesday. What's now known as "the squirrel arson," at first appeared more sinister. A man was driving his Kia Optima home from the Longmont Recreation Center on May 28 when he noticed his car was smoking, Satur said. "So, he pulled over to the side of the road and the car caught on fire," causing extensive damage, Satur said. Fire investigators brought in an arson dog named Shadow, trained to detect traces of accelerants, such as fuel, that an arsonist would use to set a fire, he said. The yellow Labrador retriever "hit on a couple things in the car," including part of the fuel line and a damaged part near the radiator, Satur said. In hindsight, investigators believe the dog was hitting on leaked fueled that occurred as a result of the fire. The plot thickened when the nervous car owner said he was writing a book about a bank fraud that would name about 500 people and feared the fire could be retaliation, according to a police report. An initial inspection of the charred car found bits of paper.Longmont Detective Wayne Rafferty obtained a warrant to search the car for evidence.Rafferty also reviewed surveillance video of the rec center parking lot, but he didn't see anyone tampering with the man's parked car, Satur said.The car owner's insurance company hired a firm specializing in fire investigations. The arson experts and Rafferty took a harder look at the damaged car."They went back and dug deeper into the car and they started pulling things apart," Satur said. The critical clue: "They found a nest made from a substantial piece of paper" in a recess of the engine, Satur said."A squirrel seems like a likely candidate" for the fire-starter, he added."The area where the car owner lives has a lot of smaller trees and squirrels tend to look for good nesting areas," Satur said. "And this squirrel may have felt that the vehicle was a good spot."He said the case highlighted the challenge of solving arson fires. "With arsons, sometimes you never can find the exact cause," Satur said."It was really some good work by Detective Rafferty and this fire investigator," he said. "They didn't jump to any conclusions. They just kept narrowing it down until they finally figured it out," he said.