Suddenly, for no apparent reason, a Volvo explodes

I heard something that sounded like what you think an explosion should sound like, and walked into the living room to see if Cleodhna had heard something like that as well. We peered out of the windows and couldn't see anything, but we definitely agreed that something had happened, so she went down to have a look. Barely had she got down there that I saw another explosion at the end of our street, and a police car arriving with blues and twos. By the time I'd fetched my phone and called 999 to make sure that they knew about the fire, a fire engine had turned up. All within, I think, 1 or 2 minutes.

Well, they put the fire out, it turns out it was a black Volvo estate that had exploded for no apparent reason, so all very good, but here's the thing that intrigues me. First of all, if the second explosion was the fuel tank, what was the first? And also: we live at number 23, and the exploding car was at the end of the street, so not far. Yet nobody in our block, congregated around the police car parked in the middle of the street, could say anything about whose car it was, even though they'd all vaguely seen it before.