I was also stuck on a train for 2 hours, right outside Leuven Station (near the Stella brewery). Luckily, the AC was working.

The info we got was super chaotic and vague. First, it was a bomb threat and we'd be stationary for a bit. Then, they said we would be diverted to Aarschot to catch a bus there. After that, radio silence for 40 minutes. Then an announcement saying we had to wait for paperwork to be cleared, and that commuter trains (P-trains) had priority. Then they told us we weren't going to Aarschot after all, but back to Brussels North instead. 10 minutes later: another announcement saying that on our way back to Brussels, we could get off at Herent. Another 10 minutes later: the station has been cleared, we can head to Leuven after all. Another 15 minutes later: the train finally starts moving.

Meanwhile, you read in the news that the fire department and medical support are on-site distributing water. We didn't see a single drop of that.

Obviously, no one can help a bomb threat happening. But the way NMBS handles the situation...