The U.S. Coast Guard is warning beachgoers to "remain clear" if they come across a silver-shaped cylinder along the shoreline, as it could be an armed flare.Coast Guard Sector Lake Michigan said in a statement three phosphorus pyrotechnic flares were unaccounted for after a joint military exercise with the Coast Guard and Air Force earlier this month offshore Milwaukee.SEVERAL PEOPLE HOSPITALIZED IN FLORIDA AFTER COAST GUARD RESPONDS TO SEPARATE HOLIDAY BOATING INCIDENTSDuring the exercise, four phosphorus pyrotechnics that were deployed did not activate when entering the water, according to officials.One phosphorous pyrotechnic was located on Montrose Beach, Illinois, by a lifeguard on May 26.A MASSIVE EXPLOSION AT AN IRANIAN PORT LINKED TO MISSILE FUEL SHIPMENT KILLS 5, INJURES OVER 700However, three phosphorus pyrotechnics are still unaccounted for.The missing pyrotechnics are still considered armed when they do not activate.Phosphorus pyrotechnics produce a red smoke and flame that can reach temperatures of 2,900 degrees Fahrenheit, according to military officials.