Poison gas kills 10,000 salmon

The regional newspaper Lofotposten says the incident took place at Eidisholmen outside Stamsund. The fish had an average weight of around two kilos.The gas is reported to be hydrogen sulphide, sometimes called sewer gas. It is colourless and known for its pungent "rotten egg" odour at low concentrations.

It is extremely flammable and highly toxic and can occur naturally under certain conditions.

According to Lofotposten, the incident affected a site owned by Isqueen a local family-owned salmon farming company. Isqueen was quoted as saying the problem first became apparent earlier this month when bubbling gas the smell of rotten eggs were observed.

Unusually high temperatures, which have caused other problems in northern Norway such as exceptionally high lice numbers at several fish farms, are thought to be behind the incident.

Production manager Henrik Svendsen told the newspaper that the deaths are believed to have been caused by the period of unusually high summer temperatures.

There have also been unusually calm seas, and a reduced water flow in the facility. The company has informed the Norwegian Food Safety Authority of the incident.

Isqueen AS is run by the Svendsen family, now in the second and third generation of salmon farmers. The company also runs its own salmon visitor centre for schools and tourists and was previously known by the name of Lofoten Polarlaks.

The company says the situation is now under control.