It is possible that there was an explosive planted, plus some sort of thermal detonator that was triggered electronically, or even that the battery was used as a thermal detonator to detonate an explosive.
While the Note 7 exploded with quite a bit of force, they never caused injuries like these, and the Note 7 likely had much bigger battery than these pagers had.
We won't know for sure until the devices have been examined.
> The official said some people felt the pagers heat up and disposed of them before they burst.
Sounds more like a battery explosion, but it's way too early to tell.