The main Jail in Baltimore, Maryland is said to be on fire at this hour. Emergency responders are classifying it as a "mass casualty incident."
There isn't much that can burn inside a jail. In most jails, but not all, there are fire sprinklers.
Smoke would end up being the big issue with this type of incident. Guys locked in cells, unable to get fresh air and needing a prison guard with keys to open each cell would add to the trouble.
Or, worse, guys NOT in cells, and so fire dept. cannot even go in because . . . well . . . you know.
More info as it becomes available . . .