Two men are being treated for serious burns injuries at Cork University Hospital following an incident at the ESB's generating station at Tarbert in Co Kerry.
A third man was injured less seriously and is being treated in Tralee General Hospital.
A "flash" was reported at 12.40 p.m. in a switch-gear room at the power station where the three men at work.
Ambulance and fire services were called immediately and the station emergency plan was put into action.
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All three were initially treated at Tralee General.
The ESB said this afternoon that it was investigating "the cause of the accident and will be co-operating fully with the Health and Safety Authority".