Though I think it is more likely that it was planted explosives - in particular given how two explosions hit the same pipeline, and one was missed - I will add that if it was a virus, CIA has a track record when it comes to software and pipelines to Europe from Russia.

CIA plot led to huge blast in Siberian gas pipeline

The breakthrough came when Vetrov told the CIA of a specific "shopping list" of software technology that Moscow was seeking to update its pipeline as it sought to export natural gas to Western Europe.

Washington was keen to block the deal and, after securing President Reagan's approval in January 1982, the CIA tricked the Soviet Union into acquiring software with built-in flaws.

"In order to disrupt the Soviet gas supply, its hard currency earnings from the West, and the internal Russian economy, the pipeline software that was to run the pumps, turbines and valves was programmed to go haywire after a decent interval, to reset pump speeds and valve settings to produce pressures far beyond those acceptable to pipeline joints and welds," Mr Reed writes.

The project exceeded the CIA's wildest dreams. There were no casualties in the explosion, but it was so dramatic that the first reports are said to have stirred alarm in Washington.