Power supplier Scottish & Southern Energy (SSE) said it cannot predict when electricity will next be generated at its Glendoe hydro power station following a partial blockage caused by internal rock falls near the top of the tunnel carrying water from the reservoir to the power station.The tunnel has been drained and SSE will now undertake a detailed investigation of its entire length and then start work on the necessary repairs. The group said it will provide an update on the progress of the investigation and the schedule for the repair work when it publishes its half-year results on 11 November.The turbine in the power station has not been affected, it added.'It is hugely disappointing that this problem should have arisen at Glendoe, when it appeared that the development of the scheme had been completely successful,' said chief executive Ian Marchant.'Extreme care will be taken with the investigation and repairs to make sure the scheme emerges from this difficulty in a strong position to operate successfully over the long term.'