Authorities in Boulder County, Colorado, haven’t ruled out arson as a possible cause of a wildfire that destroyed hundreds of homes last week. “We have a number of tips we’re working on,” Boulder County Sheriff Joe Pelle said. “We’ve executed a search warrant at one particular location we’re investigating.” Earlier, Pelle and other officials said that blown-down power lines may have been the cause of the Marshall Fire. But on Saturday, Pelle said investigators found no downed power lines as officials are now involved in “a very active investigation” that involves federal and state resources. Furthermore, Pelle said he’s not ruling out arson. “If it turns out to be arson or reckless behavior with fire, we’re taking appropriate actions,” he said. “It was a red flag day, the day of the fire, so there shouldn’t have been any burning of anything.” His office is also “actively investigating a number of tips …