Operations were suspended at a nuclear power plant near the East Sea coast of Japan after a sudden rise in a radioactive substance in its coolant.

Japan Power Engineering and Inspection Corporation, which manages the Tsuruga Number Two nuclear reactor in Tsuruga City, Fukui Prefecture, suspended operations Saturday morning (Korea time). The corporation says it will keep the plant shutdown until Saturday evening in order to identify the rise in the radioactive substance.

Experts suspect that there may be holes in the coverings of nuclear fuel rods at the Tsuruga Number Two nuclear power plant. The density of Xenon-133 rose 700 times its usual level, or 39-hundred Becquerels per cubic centimeter.

However, the corporation said that the figure is far below that required to stop operations and that the suspension on Saturday is a precautionary measure.