The Brit held off his team-mate Lewis Hamilton to take a stunning win at Spa, but this breach of the regulations could cost him his victory.
The media, including GPFans, spoke to Mercedes team boss Toto Wolff about the weight discrepancy, but could not comment until the stewards made their decision.
"It’s been reported to the stewards that there is a weight discrepancy," Wolff said.
"We will see what the stewards will decide."
Russell only made one pit stop during the Belgian GP, and Wolff was asked whether the weight issue was to do with the tyres.
"I can’t comment because the stewards haven’t given their verdict but clearly it was unexpected to run with one tyre throughout the race, so let’s see what they say," Wolff added.
"We have to take it on the chin if the stewards decide against ourselves.
"A mistake has happened, or could have happened, and 1-2 would have been a great result going into the summer break.
"The positive is that we had two cars that were the benchmark, with two different strategies, who would have said that a month ago?"
"If the stewards deem it to be a breach of regulations then it is what it is. We have to learn from that and as a team there are more positives to take."
The stewards confirmed the weight breach, and that Russell has been disqualified from the Belgian GP.