Two years after the Beslan school bloodbath, Russian forces have been criticised again for their botched operation to rescue the hostages.
The hostages' terror was clear on a video made by the gunmen
A member of Russia's parliamentary commission investigating the September 2004 siege said rocket-propelled grenades fired by the surrounding Russian forces probably led to the heavy death toll in the school gym, where more than 1,000 people were being held hostage by pro-Chechen gunmen.
The conclusions of Yuri Savelyev - a weapons and explosives expert - contradict the official view that bombs planted by the hostage-takers went off just before the gun battle.
The latest claims help to fuel speculation about a Kremlin cover-up over the three-day siege, in which at least 331 people - most of them children - died.
Many of the victims' relatives say they have lost all hope that the authorities will ever tell the truth about the siege which shocked the world.
Some of them have bluntly warned senior Russian officials not to attend the commemorations in Beslan.
The sole surviving hostage-taker to be arrested - Nur-Pashi Kulayev - was jailed for life in May. But his trial shed little light on how the tragedy unfolded.
How did dozens of gunmen, allegedly using a truck laden with explosives, manage to dodge checkpoints dotted around North Ossetia's borders?
Why did negotiations with the militants - demanding a pullout of Russian troops from Chechnya - fail?
Why did the troops fire tank shells and flame-throwers - a move many in Beslan believe resulted in the deaths of most of the hostages?
These and many other questions remain unanswered even today.
Speaking on the eve of the second anniversary of the massacre, Mr Savelyev said his technical analysis showed the gun battle in the gym began with several explosive devices - probably rocket-propelled grenades - hitting the building from outside.
"Most of the hostages were talking about explosions in a totally different part of the gym from that to which the official investigation referred," Mr Savelyev told Echo Moskvy radio.
Mr Savelyev said the blasts killed many of the hostages and dozens more died in the resulting inferno.
His conclusions were rejected by one of his colleagues on the investigating commission, Arkady Baskayev.
The commission itself has repeatedly delayed publishing its final report, admitting that the inquiry still has "many holes".
Kulayev was jailed for life in May
But its head Alexander Torshin said last year that the raid on the school could have been prevented had North Ossetia's interior ministry stepped up security around schools as requested by the Kremlin.
A separate investigation by North Ossetian lawmakers blamed the republic's law enforcement bodies for allowing the hostage-takers to enter Beslan unnoticed.
It also concluded that the Russian assault forces had used grenade launchers, flame-throwers and tank fire.
Russian officials last year admitted that such equipment had been used, after initially denying the use of flame-throwers.
Prosecutors at Kulayev's trial said 32 gunmen drove in an army truck from neighbouring Ingushetia, seizing School Number One on 1 September.
They say the gunmen brought all the weapons and home-made explosives with them.
After protracted negotiations, special forces had no choice but to storm the gym when one of the bombs accidentally went off and gunfire was heard in the gym, the prosecutors said.
They say the commandos took all possible precautions to save the hostages' lives, but heavy casualties occurred when the gym's roof collapsed, after being blown up by the hostage-takers.
Kulayev - who was found guilty of murder and terrorism - was the only hostage-taker who managed to escape, according to the prosecutors.
Mistrust in Beslan
Several former hostages and relatives of the Beslan victims challenged the prosecution's main assumptions.
Beslan mothers are determined to find the truth
They said a cache of weapons had been hidden under the school's floor in advance.
They also claim more than 32 gunmen took part in the siege and that some of them managed to escape.
The testimony of Kulayev - who pleaded not guilty to all nine charges against him - also significantly differed from the version presented by the prosecutors.
The 25-year-old Chechen carpenter said the first blast happened after a sniper killed one of the hostage-takers, who was holding a detonator.
Several survivors testified that just before the explosion they saw one of the gunmen controlling the detonator slumping off the chair.
The self-confessed mastermind of the siege, Chechen warlord Shamil Basayev, was killed in July.
He had claimed that the Russian security services bore responsibility for the carnage.
Basayev said a security service agent had been sent to the rebels to persuade them to carry out an attack in North Ossetia's capital, Vladikavkaz.
According to Basayev, the agent then tipped off the rebels about a plan to ambush them, allowing them to switch their attack to Beslan.
He said the gunmen were allowed to enter the region with ease because the security services were planning to capture them in Vladikavkaz.
Basayev also claimed that another attacker survived the siege.
Russian officials dismissed the claims as "total nonsense".