Bags containing radioactive soil, leaves and debris from decontamination work are dumped in front of a hill marked "Naraha" in Japanese in Naraha, Fukushima prefecture, Japan, February 11, 2016. REUTERS/Toru Hanai

Five years after the Fukushima nuclear disaster, concerns of contamination continue with a Greenpeace report talking of mutations in trees, butterflies and worms. Based on peer-reviewed research, it notes that the environmental impact forests around Fukushima is just beginning to be seen and will be a source of contamination for years to come.

The vast stocks of radiation in the forests cannot be decontaminated, the report adds.

The Japanese government plans to lift evacuation orders next year if the decontamination effort is successful. The Greenpeace report points to how only residential areas are being cleaned while parts of the countryside worst hit have been ignored. These could act as radiation reservoirs and re-contaminate the area, reports AFP.

The 9 R magnitude undersea quake on March 11, 2011 set off a tsunami that flooded the reactors, cutting off power to the control room and affecting the coolant system which led to meltdown at three of its six units. The hydrogen gas exploded through the reactor, releasing radioactive elements.

Thyroid cancer in young people was among the after-effects of the Chernobyl catastrophe. Experts however feel that more research is required to establish a link.

It was several hours after the earthquake that residents in some areas were informed about the nuclear meltdown. Eventually, around 400,000 people were evacuated, many of whom haven't yet returned.

Former Japanese prime minister Naoto Kan has warned in an interview with The Telegraph the nuclear accident is still going on, with radioactive water leaking out of reactors 2 and 3 that still contain the fuel rods.

The catastrophe saw the biggest ever dump of radioactive waste into the ocean when seawater was used to cool the reactor and released into the ocean.