DENVER — It could take a month to sort the offenders from the victims in a widespread sexting case at a Colorado high school, and then authorities plan to file charges only if “absolutely necessary,” a prosecutor said. An unspecified number of Canon City High School students have been suspended over the exchange of hundreds of explicit photos of students as young as eighth-graders. An investigation began Monday after some people contacted school officials and a tip came through a state student safety hotline. Three phones have been confiscated, and authorities are seeking search warrants to examine them. It remains unclear how many students posed for nude pictures and the investigation is expected to take about 30 days, Canon City Police Capt.