Six Russian state prosecutors are travelling to the southern town of Beslan to investigate the bloody siege in School Number One a year ago.
The mourning continues for the mothers of the dead
The team was sent by President Vladimir Putin after he met bereaved mothers from Beslan in Moscow on Friday.
The Beslan Mothers' Committee believes most of the 331 victims died because of the firepower used in the Russian assault on the school.
Pro-Chechen gunmen had taken civilians hostage in the school gym.
Mr Putin promised a thorough examination of all the information on the Beslan tragedy.
The team is being led by Russia's deputy prosecutor-general, Vladimir Kolesnikov.
The mothers' committee has accused the authorities of negligence, saying negotiations with the hostage-takers were shunned.
They have criticised the investigation launched last year, suspecting an official cover-up.
Beslan has just finished three days of mourning for the siege victims.
Children went back to school in Beslan on Monday - but not to School Number One, which stands as a gutted, battle-scarred memorial.
Instead classes are being held in two new schools. However, the BBC's Kirill Sukhotsky in Beslan reports that only about 70% of pupils returned to school, as many parents and children still fear another hostage-taking.