The Tokyo Electric Power Company (TEPCO), which runs the crippled nuclear plant, says levels of radioactive cesium in a water well were 9,000 percent higher on July 8, 2013, than they were three days earlier, and nobody knows why this is the case.

The Asahi Shimbun reports that TEPCO observed the spike after testing water in a well on the seaward side of Fukushima's No. 2 reactor. According to readings taken, radioactive cesium levels registered at an astounding 27,000 becquerels per liter (Bq/l), which is the highest ever since March 11, 2011, when the tsunami and earthquake first struck the plant. At this point, the cause of the spike is still unknown.