Denmark said Wednesday that it had stopped the first exploratory drilling for shale gas in the country a day after it began, accusing French company Total of using an unauthorised chemical.

"They used a product that was not part of those authorised" for the procedure, Ture Falbe-Hansen, a Danish Energy Agency spokesman told AFP.

According to Danish public broadcaster DR, the product known as Null Foam -- used in the so-called fracking process to extract shale gas -- was considered to be an environmental hazard.

"We have emphasised that the conditions stated in the drilling permit must be respected," said a director of the Danish Energy Agency, Martin Hansen, in a statement after a meeting with Total.

"We have also asked for an account of the sequence of events that occurred," he added.

Henrik Nicolaisen, who leads the drilling project for Total, said the chemical was not illegal and was left off the initial list of products used at the site "because we did not expect it would be a problem".

"We have been in dialogue with both the municipality and the Danish Energy Agency since February and we felt that we had a common understanding that the substance could be used," he told public broadcaster DR.

Total was given the go-ahead to start test drilling for shale gas in Vendsyssel in the far north of Denmark in July.

Fracking or hydraulic fracturing is a process used to extract gas or oil from shale rock by blasting a high-pressure mixture of water, sand and chemicals deep underground to release hydrocarbons trapped between layers of the rock.

Environmentalists argue that the process may contaminate ground water and even cause small earthquakes.

Denmark is one of the few European countries alongside Britain, Poland and Romania that allows fracking, which is widely used in the United States, contributing to the country's burgeoning oil and natural gas production.

Last month the German government proposed new rules to restrict fracking, citing environmental and public health concerns.