By Patrick Jackson
Russian media were already reporting the theory of a terrorist attack - later confirmed by investigators - hours after news broke that the Nevsky Express had derailed.
The Nevsky Express was carrying hundreds of passengers
Their reaction to the disaster was testament to the incident's chilling echo of a previous bomb attack on another Nevsky Express train on 13 August 2007.
That evening, at about 2130 local time, a device laid on the rails in Novgorod region blew up the train, travelling from Moscow to Russia's second city, St Petersburg.
The explosion derailed the train and some 30 people were injured.
Memories of that incident were sharply reawakened at 2137 local time on 27 November, 2009, as the Nevsky Express was derailed again, this time with major loss of life.
Russian Railways were quick to announce that one theory was that an explosion was to blame. Police sources went further, telling reporters that a crater had been found next to the track.
Later, Russian television channels broadcast a recording of a mobile phone call from the train driver to the emergencies ministry.
"There was an explosion under the locomotive," he said. "I do not know what we hit. We are derailed. The locomotive and carriages, I do not know yet what else, everything is in smoke. "
As rescuers worked through the night at the scene of the disaster, investigators hardened suspicion into fact.
On Saturday afternoon, Russia's federal investigative committee confirmed bomb fragments had been found and prosecutors said they were hunting terrorist attackers.
Any incident disrupting rail traffic between Moscow and St Petersburg must be of grave concern to the country's authorities.
One line of inquiry that investigators are now likely to pursue is that the bombing is a continuation of the attacks on public transport by Chechen militants or their allies.
That deadly campaign reached a crescendo in the summer of 2004 when bombers struck at Moscow itself, attacking airliners and the capital's metro system.
However, in the years since then, separatist militants in Chechnya and the restive neighbouring region of Ingushetia have largely confined their attacks to the North Caucasus.
The August 2007 train attack appears to have been an exception if, as Russian prosecutors allege, it was perpetrated by a group with links to prominent Chechen rebel Doku Umarov.
Two suspects are currently on trial in Novgorod, charged with carrying out that attack.
There has been no immediate, credible claim of responsibility for this latest attack.
Some believe it could raise fears of more attacks on the Russian heartland by rebels from the turbulent North Caucasus.