Allegations that the Baku metro disaster in Azerbaijan was caused by a bomb increased in volume yesterday after investigators reportedly found two mysterious large holes in the side of one of the wrecked railway carriages.
Azeri national television last night quoted experts who said the holes pointed to the use of an explosive device.
The allegation was that the bomb was charged with poisonous gases which killed many of the victims.
In Moscow, the Russian news agency Itar-Tass quoted sources who said that the bombing was "to aggravate the social and political situation" in the republic in the run-up to parliamentary elections on 12 November.
This has been the focus of political dissent in the unstable former Soviet republic.
At least 289 people were killed and 269 hurt when a fire broke out a train on Saturday while it was in a tunnel between two stations in central Baku, an oil city of 1.8 million people on the western shores of the Caspian Sea.
At first, the Azeri government commission of inquiry investigating the disaster concluded that it was caused by an electrical fault and blamed outdated Soviet-era equipment, but since then the authorities have begun to entertain the possibility of sabotage.
The theory is being taken seriously, not least because 20 people have died in two bombings in Baku's metro system in the last 18 months, but the picture is complicated by the suspicion that the metro's operators may be trying to blame a non-existent saboteur in order to avoid being held responsible themselves.
Adding weight to this theory, a fire broke out yesterday on the Baku underground after a train engine caught fire at the Kara Karayev station.
The Deputy Prime Minister, Abbas Abbasov, said the fire was put out promptly by station workers.
Officials have said many of the victims of Saturday's disaster were poisoned by gases released as flames swept through the tunnel.
Azeri national television - which has been under strict government control since the tragedy - quoted experts saying that poison was used in the bomb.
If so, the disaster would be a repetition - on a terrifying scale - of the poisoning of passengers in the Tokyo metro in March, allegedly by a religious cult, in which 12 people died.