Elevated concentrations of caesium-137 and caesium-134 isotopes bearing the characteristic signature of the Chernobyl blast were found especially in southern Germany, the federal office for consumer protection and food safety (BVL) said.

However, none of the 74 samples tested exceeded the legal limit of 600 becquerels of radiation per kg.

The Chernobyl reactor, located in what is now Ukraine, spewed tonnes of nuclear waste into the atmosphere, spreading radioactivity across swathes of the continent and causing a spike in cancers in the more immediate region.

The BVL said the radioactive material lingered in forests because their ecosystems recycled nutrients so efficiently, meaning that wild mushrooms will show contamination for much longer than other agricultural products.

Concern at the long-term impact of nuclear disasters has fuelled public opposition to nuclear power, and in Germany triggered a decision, shortly after the accident at Japan’s Fukushima plant in 2011, to abandon it altogether.