Not in a position to watch those at the moment, but I recall my first views of video of this, and I do recall a lesser blow-up before the big blast. If I can find it again I’ll post it.
Or I could be mis-remembering it.
I don’t know if the distances work out, but the sound wave from the earlier, whitish explosion/conflagration (which may not have produced a shock wave or produced a much weaker one that petered out quickly) would have been running ahead of the faster shock wave of the second, much larger explosion. The first bang was certainly loud enough that people looked around and started filming the white cloud and therefore caught the bigger explosion on camera.
Assume the first bang was ~20 seconds ahead of the larger boom, which starts out moving much faster but slows over time. There might be some radius from the blast where the first bang is only around a second ahead of the shock wave. That’s only if the shock wave from the second explosion travels for a long way before slowing to sonic, though. 20 seconds is a long head start at the speed of sound.
Sounds (ha!) to me like quite plausible. Similar with the footage from the church, first a tremor that makes people look around like “what was that” and in seconds a blast that wrecks things and makes them run.
Yep - if you watch the BBC video (a reporter was on a video call when the event occurred) - the scene shook visibly; the reporter stood up and went to look out of the window, just in time for the blast wave to hit and blow the glass in at her. Sound travels faster through solid ground than air
There were more than thirty seconds between the two explosions (the smaller, though still substantial, first one and the much more powerful second one). In the video it’s only one or two seconds between the sound the OP asks about and the main blast. So it can’t have been the first explosion.