According to Sucre, T-Bag did start with a fire in Sona, killing this a lot of inmates. This even did lead to escape from T-Bag, Bellick and Sucre out of Sona. Only a few Sona inmates survived, making also their status unknown, because it's unknown what happened to them.[1] According to IMDB was there an actor who played Sona Inmate 143.[2] That did mean that there were at least more than 50 dead, because of the fire by T-Bag.
There are at least 76 inmates who's fates is unknown and not shown on-screen. Also notice that the inviduals from Sona are count as well, and mostly every episode of Season 3 had a lot of inmates per episode.
It's not revealed how many inmates died during T-Bag's riot, but Lincoln mentioned that it hadn't the names of Sucre, Bellick and T-Bag at all.[3]
Pistachio and Mariano are the only names unknown victims of T-Bag.
According to Lincoln the inmates in Sona started a riot. However, he didn't know that this was because of T-Bag, who started the riot after Michael's escape (The Legend).
T-Bag also could have unknown victims by the drugs he could give to other inmates as well, who died off-screen in a cell.