LiIon batteries can burn and “explode” quite violently so if there’s a way to remotely hack the devices’ firmware and if the batteries in the devices are cheap and don’t have any additional protection circuitry that makes them stay within safe parameters, I can imagine that there is a way to trigger an unsafe condition.
Many people tend to carry their pager in their trousers, close to the body, so a battery burning violently could do a lot of damage.