First images from inside the ruins of Fukushima's nuclear reactor show 'icicle-like' formations

Investigators have shared new images from inside the stricken Fukushima nuclear power plant in Japan.

In 2011 the Fukushima Daiichi nuclear power station suffered a major incident, being shut down and an exclusion zone put in place.

It came shortly after the Tōhoku earthquake and tsunami which devastated huge portions of Japan's coast and killed almost 20,000 people.

But things became more complicated when it emerged that the earthquake had damaged the power plant's backup energy sources. This meant that the plant was unable to cool the reactors properly after shutdown, which resulted in a breach to its containment of radioactive materials.

When the reactor was operating coolant would continually be pumped into the reactor core to keep its temperature stable.

The disruption to this process caused a full meltdown in the reactor after immense heat built up.

Today the plant is off limits, and is highly dangerous to enter due to the quantity of radioactive material in there.

However, a team of investigators have managed to get a look inside by using a robot.

The snake-like robot was sent into Fukushima accompanied by mini drones to get a look at how things are inside.

And the images indicate that there is still a long way to go on the cleanup operation even 13 years after the incident.

A look inside the stricken reactor. (TEPCO)

Operations are being overseen by the Tokyo Electric Power Company Holdings (TEPCO), also the company which operated the plant.

The aim of the expedition inside was to learn more about the condition of the plant and the spent fuel so they can better carry out cleanup operations on the site.

In the images you can make out strange 'icicle-like adhesions', as well as 'clump-like objects' hanging from the reactor's walls.

These are the first images to be taken inside the 'pedestal' of reactor Unit 1.

They found icicle-like structures inside. (TEPCO)

The company said that 'very useful information has been obtained' following the investigation and they will 'analyzing the videos taken by the small drones'.

The cleanup operation has made progress, but has also met with controversy of its own.

This was focussed around TEPCO's decision to dump treated water from the plant into the Pacific Ocean.

Even though multiple agencies said the treated water would be safe to release, the decision did not sit well with many people concerned about the impact it could have despite being treated.

The interior of the plant has also become known as a 'robot graveyard' due to the number of robots that have broken down inside.