BOULDER CITY, Nev. (AP) — Authorities say six people have been injured, but only one seriously, after an explosion and fire at a commercial manufacturing plant southeast of Boulder City. The explosion occurred just before 10 a.m. Monday. City police and fire crews plus personnel from the Henderson Fire Department were sent to the Armorock Polymer Concrete facility on U.S. 95. The cause of the explosion isn’t immediately known. Authorities say the plant was being evacuated and seven employees had been transported to area hospitals. The conditions of the injured employees weren’t immediately released. Armorock Polymer Concrete is located in an industrial area some 7 miles southeast of Boulder City along U.S. 95.