on 11 january 2012, radioactively contaminated water was found in two tunnels. on 12 january, tepco admitted that around 300 cubic meters of water had accumulated in a tunnel near reactor no.3, with electric cables. radioactive caesium was measured in concentrations varying from 49 to 69 becquerels per cubic centimeter. smaller amounts of contaminated water with lower concentrations caesium was found in a tunnel near reactor no.1. how the water could accumulate at these places was under examination.