The world’s largest atomic plant in Japan has trouble with a pair of fuel rods that were touching as a result of a deformation in a bundle of rods in a fuel pool, reported ABC News.

The Japanese regulator said the deformation could have caused the rods to heat up, and it described it as a level-one incident – the lowest on the seven-point international scale.

The nuclear power facility has seven reactors and is operated by Tokyo Electric Power Company (TEPCO), which also operates the Fukushima nuclear plant.

Five of the seven units have 1100MWe capacity each, while the remaining two have 1356MWe electricity output each, according the company’s website.