Officials at the plant had reported that part of the reactor core was exposed to air for a brief moment and that they were attempting to raise the water level to continue cooling the reactor. Officials later stated that steam was vented from the power plant to release the pressure built up by evaporating water. If an explosion occurred, it would indicate that the additional water pumped into the reactor has been unable to stave off the meltdown reaction inside the reactor core and that the plant is experiencing a far more serious crisis than initially reported by the Japanese authorities.