Early launch is seen among the most probable causes of the recent Proton-M rocket failure and the loss of three satellites, a space industry source familiar with the investigation said.
The undisclosed source said a special commission continues to investigate the failure and several versions are being considered.
He said that one possible version is that, "for yet unknown reasons, an early start took place and resulted in the failure." The rocket's control system treated the early start as an emergency situation and started to divert the rocket away from the launch pad to a safer distance, as it is programmed to do, he said.
"This version now prevails," the source said, adding that other versions are also being carefully studied.
He said specialists are now working to decipher telemetry data, and it might take days to be completed.
The Proton-M rocket was carrying three Glonass navigation satellites when it exploded shortly after launch early on Tuesday from the Baikonur space center in Kazakhstan. The accident is the second unsuccessful launch of a Proton-M rocket carrying satellites for Russia's flagship Glonass positioning system in the last three years.