Bulgaria's government banned over environmental concerns U.S oil company Chevron from using hydraulic fracking when exploring for shale gas in the country.
For the time being, there is no sufficient data that the method of hydraulic fracturing, or fracking, used in shale gas exploration and extraction is environmentally safe, the government said in a statement.
However, Chevron can still prospect for gas and oil in Bulgaria using conventional drilling techniques, the government added.
In July 2011 the Bulgarian government granted the company's local unit, Chevron Bulgaria Exploration and Production, a five-year licence for gas and oil exploration in the 4,398-square kilometre Block 1 Novi Pazar in northeastern Bulgaria.
Two months earlier Bulgarian media reported that the U.S. group planned to invest 30 million euro ($38.4 million) in the southeast European country.
Following environmentalists' protests against shale gas exploration and extraction in big cities across the country over the weekend, Bulgaria's Parliament is expected to vote on a bill envisaging the introduction of a temporary ban on hydraulic fracturing later this week.