LYNN – Police are questioning several “persons of interest” as they investigate three seemingly related October pipe bomb incidents that have left city residents on edge.A task force comprised of Lynn and Swampscott police and fire investigators, state troopers and federal agents from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) have narrowed the search to a handful of suspects.Police Chief Kevin Coppinger said a meeting of all investigative agencies was held Tuesday to discuss information gleaned during interviews with suspects as well as evidence gathered from the three incident scenes.”There are a number of persons of interest who we have been talking to. The evidence collected is being analyzed at the State Police crime lab,” he said, noting that detectives are awaiting the results.Coppinger said it’s likely the three incidents are related, given that all involved pipe bombs and occurred relatively within the same area. The first incident on Oct. 11 involved an explosive device found on Hillside Avenue in Swampscott. It was followed by the Essex Street explosion on Oct. 13 that damaged the vehicle but caused no injuries. The third pipe bomb was discovered by a homeowner on Oct. 16 at the rear of 80 Collins St., attached to a propane gas grill. It was fitted with green electrical wires. The neighborhood was evacuated as the device was detonated by the State Police Bomb Squad.The bomb-disarming experts were again dispatched to Lynn on Monday when passersby at Red Rock Park spotted a knapsack that appeared to contain an explosive device. Coppinger said police found a bottle of vodka and an orange juice mixer inside the backpack, which belonged to an intoxicated Plymouth man.Coppinger said public nervousness generated by the incidents, particularly the second in which a pipe bomb exploded inside an automobile in front of 3 Essex St., is understandable.”We do live in a post-9/11 era,” the chief said, adding that residents are urged to contact authorities if they spot any activity of a suspicious nature.Police Capt. Mark O’Toole and Lt. Thomas Reddy are heading up the investigation for Lynn police. Anyone with information can contact the police by calling the 24-hour tip line at 781-477-4444 or send a text message to TIP411 or 847411, with the words Tip Lynn in the body of the message, followed by a space and the information.Coppinger said police have no way of knowing who left the text message. “It’s a great tool, and the messages are monitored by the commanding officers and myself, but it’s not for use in emergencies. For that, you call 911,” he said.