Plutonium has been detected in soil samples taken in five locations at Japan’s Fukushima nuclear plant No. 1, the Tokyo Electric Power company (TEPCO) said on March 28.

According to the nuclear complex’s operator TEPCO, this was the first time plutonium had been detected at the nuke plant since the March 11earthquake and tsunami that devastated the plant’s reactors.

Of the samples from five locations, there is a high possibility that at least two of them are directly linked with the current reactor accident, TEPCO spokesman said.

Plutonium is more noxious than other radioactive substances like iodine and cesium, but TEPCO said the level is not serious enough to harm human health.

Hidehiko Nishiyama, a spokesman for the Japan Nuclear and Industrial Safety Agency, the detection of plutonium showed the damage of fuel rods. TEPCO an the Ministry of Science will keep a close watch on the environment at the plant and its surrounding areas within a radius of 20km.

Earlier the same day, TEPCO said, high levels of radiation exceeding 1,000 millisieverts per hour have been detected in water in a trench outside the No. 2 reactor's building at the nuclear plant, with the contaminated water suspected to have come from the reactor's core, where fuel rods have partially melted.

The radiation level in the air in the trench stood at 100 to 300 millisieverts, the company said.

At a radiation level of 1,000 millisieverts per hour, people could suffer a decrease in the number of lymphocytes -- a type of white blood cell -- in just 30 minutes, and half could die within 30 days by remaining in such conditions for four hours./.