A specially-designed robot has become stranded after capturing the first grainy images from inside one of the melted reactors at Japan’s doomed Fukushima nuclear plant.
It withstood the deadly radioactive environment but then became stuck two-thirds of the way through its mission and had to be abandoned.
Pictures lit by a lamp on the robot showed steam wafting around the chamber and debris that looked like small rocks and metal parts.
The video also showed numerous white spots believed to be caused by gamma rays.
Despite the glitch, officials said the images were a success and showed it was possible to send in more sophisticated robots as they embark on a 40-year mission to make the plant safe.
The robot also picked up lower than expected radiation readings, according to Tokyo Electric Power Company (TEPCO), possibly paving the way for wireless devices to explore the site.
However, radiation levels inside the plant are still far too dangerous for humans.
The 60cm Hitachi robot entered the disaster zone through a pipe and then morphed into a crawler device, collecting radiation and temperature data as it crept along.
TEPCO spokesman Teruaki Kobayashi said its journey had been halted possibly after one of its tyres got stuck in a grating.
A different amphibious robot is set to enter the site next year for more tests.
Large volumes of cooling water continue to leak from the damaged reactors, causing contamination and hampering the cleanup process.
A £1.8bn ice wall extending down 1,500 metres is hoping to freeze the earth around the wrecked plant and stop contaminated water leaching into the sea.
The nuclear meltdown in March 2011 was the worst since Chernobyl and happened after a magnitude 9 earthquake hit the area and triggered a deadly tsunami.
Three reactors at the plant went into meltdown and hundreds of thousands had to be evacuated.
So far, more than 1,600 people have died from health complications brought on by the disaster.