I wouldn't call it "confirmation" at this point, but emergency services have been reporting the discovery of "secondary devices", so it does appear to be something intentional and not something along the lines of an accidental gas line explosion.
Honestly, I would wait for the evidence that those were actually bombs. It sounds like it could have been terrorists, but it also sounds like it might have been a utility failure of some sort, like this:
Now, there are reports that the police have found additional bombs and are dismantling them; if true, then that would mean that this is an attack of some kind and not just an accident. Still, I would wait for a reliable, official statement before jumping to conclusions.
[Edit: Looks like there is now some kind of official statement from the fire department about finding additional bombs, so I guess that settles that.]
Listening to BFD radio, you hear a lot of chatter about additional "secondary devices" and "suspicious packages" even now. Apparently they have a large group of bomb-sniffing dogs they are moving around to check these things out.
