The ship was a product carrier. While maneuvering in Malacca Straits, it was noticed that one of the main engine unit’s air starting valve was leaking badly. The crew were mustered for changing the valve. Master on arrival a safe place, anchored the vessel. For testing the anchor holding, the master gave a astern movement. C/E obeyed and on giving the astern start, the air starting line exploded. The explosion was quite severe, and all the ER personnel, ran off from the engine room. Three of them injured with 2nd degree burns. C/E decided to flood the ER with CO2. All reported to the muster station, after head count and other formalities, the ER was flooded with CO2. Boundary cooling continued, till the fire experts came. After putting off the fire, the ship was towed to Singapore, for repairs.