After weeks of investigations into the allegations, the top U.S. general in Afghanistan said that he remains unconvinced by intelligence suggesting that Russians had offered bounties to Taliban militants to kill U.S. soldiers in Afghanistan.

“It just has not been proved to a level of certainty that satisfies me,” Gen. Frank McKenzie, the commander of the U.S. Central Command, which oversees Afghanistan, said in an NBC News interview on Monday. “We continue to look for that evidence. I just haven’t seen it yet. But … it’s not a closed issue.”