NEW : Besides radioactive iodine , high levels of mercury are also detected . A Tokyo Electric official says it 's not known what caused the mercury spike . Samples taken Friday morning from a monitoring station 330 meters off the coast were significantly higher than results from the previous morning , when the level was 104 times above normal . Level in seawater near nuclear plant tests three times above normal . Level detected in tap water in Ibaraki is now considered safe .
NEW : Besides radioactive iodine , high levels of mercury are also detected . A Tokyo Electric official says it 's not known what caused the mercury spike . Level in seawater near nuclear plant tests three times above normal . Level detected in tap water in Ibaraki is now considered safe .