The operator of the Fukushima Daiichi nuclear power plant has cancelled Tuesday's operation to send a remote-controlled probe into the crippled No.1 reactor.
Tokyo Electric Power Company began preparations in the morning to send the robot into the containment vessel of the reactor to monitor melted nuclear fuel.
But the company called off the attempt after images on a camera placed outside of the containment vessel to monitor the robot could not be seen on screens in the control room.
The company plans to investigate the cause of the problem and try again on Wednesday or later.