An explosion was heard Tuesday at Japan's tsunami-hit Fukushima Daiichi nuclear plant, but no rise in radiation levels nor any injuries were reported, the plant operator said.
Tokyo Electric Power Co. (TEPCO), which has struggled to control the crippled Fukushima plant, said the explosion was heard as unmanned heavy machines worked near the unit four reactor building.
"The machines were remotely controlled to remove rubble when the blast was heard," a TEPCO spokeswoman told AFP.
"Local workers believe a gas cylinder might have been damaged and caused the blast noise," she said. "No one was injured as it was a remotely controlled operation. No changes in radiation levels were detected in the area."