Source: ZDNET UK A battery fault may be responsible for an overheating problem that has affected at least three O2 handsets Mobile operator O2 is recalling over 100,000 of its X1 mobile phones after customers reported that their handsets had melted while being charged. O2 published adverts in several national newspapers on Thursday, urging X1 users to return their handsets. An O2 spokeswoman told ZDNet UK that three customers had contacted the company to report that their X1 had overheated while charging. O2 believes that the fault lies with the handset's battery, but it is still conducting investigations. O2 estimates that around 140,000 X1s are currently in circulation in the UK. O2 is the only operator that has sold the phone, which was built by a Far Eastern manufacturer and launched in 2003. The handset is no longer sold by O2 in the UK. Customers who return their X1 to O2 will be receive an X2i handset as a replacement. They need to move fast — O2 will impose a call bar from 27 March that will prevent them from making or receiving calls. "We have sent a text message out to all users, and today's newspaper adverts are the second stage. We hope that all our users are now aware of the issue," said the O2 spokeswoman. Although O2 isn't planning to offer compensation to users who have to return their phone, the X2i is a more recent handset so customers are effectively getting a free upgrade, although they may be without a mobile phone for an unspecified amount of time. X1 owners should contact the company on 0800 902 0212, or visit O2's X1 help page.