Government on Thursday said it was reviewing processes and procedures at all nuclear power stations following the "deliberate" contamination of drinking water at the Kaiga Atomic Power Station (KAPS) in which 92 employees suffered radiation.

Making a suo-motu statement in the Lok Sabha, Minister of State in PMO Prithviraj Chavan there was no security breach or damage to KAPS and "all the plant systems are operating safely."

He said there was no radioactivity release in the environment due to the incident of drinking water contamination at Kaiga, which has been described as "mischief by an insider".

An interim report of an internal probe by Nuclear Power Corporation indicated possibility of mischief by an insider who had deliberately added some heavy water containing tritium to the drinking water cooler, he said.

"As regards the investigation, the local and central agencies are at work and the evidence like log books, close circuit TV footage, analysis of water samples etc are being used to ascertain the facts," he said.

Chavan said on November 24 urine samples of employees working in the combined service building for reactor units I and II showed higher than normal traces of tritium, a heavier isotope of hydrogen.