A mining company has halted drilling for shale gas in England after scientists said two small earthquakes might be linked to the controversial process, known as "fracking."
The British Geological Survey recorded a 1.5 magnitude quake Friday near Blackpool in northwest England, within 1.2 miles (2 kilometers) of the gas exploration site. A 2.3 magnitude quake was recorded last month.
The geological survey's head of seismology, Brian Baptie, said Tuesday that the two quakes appeared to have "a similar location and mechanism."
Cuadrilla Resources said it had stopped hydraulic fracturing, or fracking _ the process of extracting gas by pummeling rocks deep underground with high-pressure water, sand and chemicals _ while it studied data from the quakes and consulted with experts.
"We expect that this analysis and subsequent consultation will take a number of weeks to conclude and we will decide on appropriate actions after that," said chief executive Mark Miller.
Shale gas extraction, pioneered by the U.S. and Canada, is forecast to boost global recoverable natural gas resources by 40 percent. But ecologists are alarmed by its environmental impact.
The biggest worry is that cancer-causing compounds used in the process could pollute water supplies. High levels of methane gas also have been found in tap water near some U.S. drilling sites, with YouTube videos showing people apparently setting fire to tap water.
Like the United States, European nations are keen to reduce their reliance on imported oil and gas. But they have been wary of fracking.
Poland has announced a major investment in shale gas to break free of dependence on Russian gas imports, but France put a similar project on hold and has taken a first legislative step toward banning shale gas extraction. Germany has some test projects, but many in the country have concerns about the environmental impact.
Last week British lawmakers said the country should develop its shale gas resources to reduce reliance on imported energy supplies. The House of Commons Energy and Climate Change committee said there was little risk to underground water aquifers as long as drilling wells were constructed properly.
The Cuadrilla exploration scheme, which began in March, is currently Britain's only shale gas project.