We recently attended a domestic fire which we believe was caused by a mobile phone overheating whilst being charged.
The mobile phone was sitting in or on a handbag which in turn was placed on a pair of chairs.
As is obvious from the photo the heat build up was significant enough to cause combustion to take place, enough to cause a significant fire.
It is important that mobile phones are not covered or insulated in any way whilst charging and the heat caused by the charging process is allowed to dissipate. We would also suggest that mobile phones are unplugged after charging and not left plugged in overnight. Make sure that your charger is a genuine charger for the make of your phone.
As always we recommend that you have working smoke alarms in your home to alert you if things do go wrong. Luckily in this case, there was no injuries, however significant damage was caused to the dwelling.