Investigators are questioning several workers following the leak of a radioactive substance into drinking water at an Indian atomic plant, according to officials.
The government has said it believes the contamination was deliberate.
The government-run Nuclear Power Corporation has launched a probe on how tritium seeped into a water cooler, which put 55 workers into medical care for excessive exposure to radiation, reports Reuters.
The leak may raise security fears over India's nuclear energy programme, though both the government and the director of the plant have played down the threat of the leak to the public.
"Investigations are being carried out to find out how it happened and who did it," an unidentified plant official told Reuters.
The plant is in Kaiga on the west coast, 450km (280 miles) from Bangalore.