However, "we have noted that there are some aspects which may raise questions with respect to that crime... but we have not yet put in any conclusion here", he said.
Asked about specific accusations of genocide, including the forced transfer of Ukrainian children to areas under Russian control, Mose said: "We are absolutely aware of these possibilities, and we will pursue this if our mandate is being prolonged.
"Based on the evidence that we have been able to achieve since actually August last year until now, we have to go step by step and that is the reason why we are at the stage where we are.
"Where we will go depends on what we will find."
In its first report, the investigative team created by the UN Human Rights Council a year ago determined that Russia had committed a vast array of violations since its full-scale invasion of Ukraine in February 2022.
Russia's forced transfer and deportation of Ukrainian children to areas under its control amounts to a war crime, the investigators said, also warning of possible crimes against humanity.
The three-person commission headed by Mose was created last year, and the UN Human Rights Council will decide early next month whether to extend its one-year mandate.