Being in IT and having worked on asics, breadboard design, lsf, dgx and others for a storage chip design company, it’s not exactly rocket science to overload a small battery so much it heats up above 140’'F/60’C that it combusts.

Here’s the initial report:

https://www.lbcgroup.tv/news/lebanon-news/796406/understanding-the-pager-and-how-it-can-explode/en