Three types of plutonium have turned up amid the radioactive contamination on the grounds of the earthquake-damaged Fukushima Daiichi nuclear power plant, its owner reported Monday.

The plutonium is a byproduct of nuclear reactions that is also part of the fuel mix at the damaged No. 3 reactor.

It was found in soil at five different points inside the plant grounds, the Tokyo Electric Power Company said late Monday.

Plutonium can be a serious health hazard if inhaled or ingested, but external exposure poses little health risk, according to the U.S. Environmental Protection Agency.