Four years after the Fukushima Daiichi nuclear disaster, a specially-designed robot with video capabilities has ventured inside one of the reactors. Unfortunately, after just three hours, it malfunctioned.

The purpose of the project was to probe the No. 1 reactor to retrieve radiation readings and gauge structural damage to the facility. The hope is that in the future, there will be a safe, efficient means by which to clean-up the melted reactors. The Tokyo Electric Power Company (TEPCO) provided the footage, delivering on their promise to release all new Fukushima data they gather.

To get inside the main reactor, the robot shifted into a snake shape to slither its way through a 10 centimeter in diameter pipe. Once through the pipe, it transformed back into a U-shape to film its surroundings. The yellow numbers displayed at the bottom of the screen are the sieverts (units of radiation absorption) per hour. At one point, the shape-shifting robot recorded 9.7 sieverts per hour—enough to kill a human within 60 minutes, according to ABC News.

The mission was intended to last 10 hours, but the robot broke down sooner than expected. The cause of the robot’s malfunction is unknown at this time, but TEPCO has said that the robot got stuck and stopped working. They are now investigating the cause before a different robot enters the site for further tests next year.

To see the remote-controlled robot in action prior to its foray into the radiation-contaminated disaster zone, click here. To view the grainy footage from inside the Fukushima reactor, watch below: