Reuters: Indian officials are investigating the leak of a radioactive substance into drinking water at an atomic power plant in the south of the country, they said on Sunday. Local police have been asked to help probe how tritium seeped into a water cooler, after which 55 workers underwent medical treatment for excessive exposure to radiation. Officials at the highly protected plant in Kaiga on the west coast, 450 km (280 miles) from Bangalore, said the leak may have been …