Workers have entered the reactor building of Unit 1 at Japan's damaged Fukushima Daiichi nuclear power plant for the first time since just after the earthquake and tsunami which devastated the site.
The plant's operator Tokyo Electric Power said workers are installing six ventilation machines in an attempt to absorb radiation from the air inside the building. The work is expected to take up to five days.
The utility must lower radiation levels inside the reactor before it can proceed with installing cooling systems, which were knocked out by the quake and tsunami on March 11.
Workers have not gone inside the reactor building since it was damaged by a hydrogen explosion on March 12.