(Adds detail) NEW YORK, Jan 8 (Reuters) - An explosion at American Electric Power Co. Inc's <AEP.N> Muskingum River coal-fired plant in Ohio killed one person and injured nine on Monday, leading to the shutdown of a coal unit, AEP said. The blast occurred as hydrogen was being delivered by truck, killing the driver, spokeswoman Melissa McHenry said. Nine AEP employees were taken to hospitals for treatment but none of the injuries was serious, the company said. Muskingum River Unit 5, rated at 585 megawatts, has been shut pending an investigation, AEP said. The other four units, totaling 840MW, are on-line. The explosion occurred outside the plant's walls, and while the cause was unknown it did not involve the unit's boilers, AEP said. (Additional reporting by Matt Daily and Eileen O'Grady)
