Do they have the ability to get to a place that is not as hot? Is the temp being measured at the ground? I am just trying to think of other things to check. Having 48 die all at once seems very suspicious. Weird poops or anything?
How many were there? Sounds more like a heat/cold issue. Like they either got cooked, or froze. If we are talking only a few then maybe it was a disease or coincidence that they all died at the same time. But if you had a large number, a disease seems less likely to kill them all at the same...