BBC: Indian officials are investigating the leak of a radioactive substance into drinking water at an atomic power plant in the south of the country. Fifty-five workers at the Kaiga plant needed medical treatment for excessive exposure to radiation after tritium contaminated a water cooler. Officials said the leak might have been deliberate. “Mischief is not ruled out. Investigations are on,” plant director J P Gupta told Reuters news agency. The 55 workers had …