Four workers were killed and seven others were injured Monday when steam leaked from a nuclear reactor in Mihama, Fukui Prefecture, in Japan's worst nuclear plant accident, rescue officials said.

According to information received by the Nuclear and Industrial Safety Agency in Tokyo, the leak took place at around 3:28 p.m. at a facility housing the turbines for the No. 3 reactor at Kansai Electric Power Co.'s Mihama Nuclear Power Plant.

Local authorities and Kepco officials said the deaths and injuries were probably due to exposure to high-temperature steam. Of the seven listed as injured, two were in serious condition, according to the Fukui Prefectural Police.