The lake is cherished as one of Russia's environmental jewels
Russian police have raided the offices of an environmental group after it criticised a plan to reopen a paper mill next to Lake Baikal in Siberia.
Several computers were confiscated by police, who said they were checking the alleged use of unlicensed software.
A member of the Baikal Environmental Wave group said the raid was linked to its efforts to keep the mill closed.
Last week Russian PM Vladimir Putin decreed that the mill could reopen. It was shut in 2008 amid pollution fears.
The lake, nicknamed "the Pearl of Siberia", is the world's largest body of fresh water and home to many unique species.
The Baikalsk Paper and Pulp Mill is the biggest employer in Baikalsk, a town of 17,000. The mill is owned by Russian billionaire Oleg Deripaska.
Environmentalists have fought for years to keep the mill shut, arguing that it threatens the lake's fragile ecosystem.
Mill managers insist they can operate the plant without polluting the lake.