The source, requesting anonymity, said a special commission was investigating why the rocket carrying three Glonass navigation satellites veered off course and exploded shortly after launch Tuesday from the Baikonur space center in Kazakhstan.
Several possible scenarios are being investigated, the source said.
"One of them is that, for yet unknown reasons, an early start took place and resulted in the failure. The control system treated it [the early start] as an emergency situation ... and started to divert the rocket away from the launch pad, to a safer distance, just the way it was programmed.
"This version [of events] now prevails," the source said, adding other possibilities are also being carefully studied.
The incident was the second unsuccessful launch of a Proton-M rocket carrying satellites for Russia's flagship Glonass GPS system in the last 3 years, RIA Novosti said.