The robots sent in to investigate the nuclear fallout at Fukushima just aren't good enough.

Tokyo Electric Power Company's (TEPCO) head of decommissioning admitted on Thursday that more creativity was needed in developing its robots sent to the reactive zone.

The Fukushima nuclear power plant was massively damaged in 2011, when three of the six nuclear reactors suffered meltdown after being struck by a 9.0-magnitude earthquake and associated tsunami waves.

More than 100,000 residents of the nearby Fukushima Prefecture had to be relocated, and the government has spent the last five years struggling with the aftermath. The incident is regarded as the world's largest nuclear disaster since Chernobyl.

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Part of the clean-up includes robots, sent in to probe the site, because radiation levels are too high for humans.

But earlier last month, a robot sent into Fukushima's No. 2 reactor was forced to abort its mission after it was blocked by deposits — believed to be a mixture of melted fuel and broken pieces of structure.

Two previous robots had also failed in its missions after one was stuck in a gap and another was abandoned after being unable to find fuel during six days of searching.

This is an example of one of the robots TEPCO had sent to probe the area in the past.

"We should think out of the box so we can examine the bottom of the core and how melted fuel debris spread out," TEPCO Head of Decommissioning Naohiro Masuda said.

Mr Masuda also added that he wants another robot sent in before deciding on methods to remove the reactor's debris.

Despite the failed probe missions, officials have added that they want to stick to their schedule of starting the site clean up in 2021.

Decommissioning the site is expected to cost tens of billions of dollars and last around 40 years.

Fukushima's No. 2 reactor was found in February to have a radiation level of 530 sieverts.

Exposure to four sieverts is enough to be lethal, according to the National Institute of Radiological Sciences.

South Korea's low-cost carrier Jeju Air also announced on Tuesday that it would not use Fukushima Airport due to fears of radiation.

Some of its customers had reportedly posted online that they would not use the airline because they didn't want to "board airplanes that flew over Fukushima."