About 55 employees working in Kaiga Nuclear Power Plant in Uttara Kannada district suffered minor nuclear radiation after drinking contaminated water in the plant.

The employees working in the first maintenance unit of the plant were treated for increasing level of tritium after they drank water from a water cooler in the operating area on November 24, official sources told PTI on condition of anonymity.

Tritium, also known as Hydrogen-3, is used in research, fusion reactors and neutron generators.

Urine examination of the employees in the unit is done everyday as a matter of routine and during such a test four days ago it was found that the tritium level was more than the normal level. They were taken to the plant hospital in Mallapur and were treated immediately, they said.

"The contents of the water in the cooler are being investigated," sources said.

Scientists carried out immediate checks for radioactivity at the plant site but no leakage was detected, sources said.

A probe was being carried out to find out how the water in the cooler was contaminated, the sources said.

KAPS-I has been shut down since October 20 for annual maintenance.

Kaiga has three atomic power units of 220 MW each. A fourth unit is almost ready for commissioning.