In the small German village of Bothel, near Bremen, the recent publication of epidemiological findings that cases of leukemia and lymphoma in men in the years 2003 to 2012 were twice as high as could have been expected is raising the already elevated temperature of the anti-fracking movement.

It is also fueling fears in the town of 2,400 inhabitants that gas production using conventional fracking methods may have triggered the rise in the cancer cases.

Adding to the concern is the discovery of higher mercury levels by the mining authority in the state of Lower Saxony, to which Bothel belongs. Many villagers are said to suspect that benzene and mercury contained in hydraulic fracturing (fracking) fluids may have risen out of the borehole and presented a health hazard.

Anti-fracking groups, contending that mercury readings by the conservationist pressure group Nabu were higher than those of state authorities, is stepping up its investigation. The groups have urged Germany to resist any attempts at widening the limited amount of fracking taking place in gas fields.

Lower Saxony's Green party environment minister, Stefan Wenzel, said the state would examine all fracking sites and impose stricter regulations where needed.

In response to a parliamentary inquiry, the coalition government of Christian and Social Democrats said it was unable to say at present whether the cancer cases were related to the fracking activity.

In July of this year, the coalition parties in Berlin agreed on a fracking moratorium until 2022, covering unconventional shale and coalbed gas deposits up to 3,000 meters, while granting exemptions for research and development projects.