Injuries: The exploding phone caused injuries so deep that doctors could see Hanghang's jawbone . A 12-year-old in central China was seriously injured when his phone exploded while it was charging. The boy, known only as Hanghang, was using the old handset as an alarm when he woke up early for school and started to play with it. He said the phone felt hot and then blew up in his face, exposing part of his jawbone and embedding fragments in his arms and legs. 'I played with the phone for a few minutes,' he said. 'The phone felt hot then it suddenly exploded and all I could see were my hands covered in blood and blood dripping from my face. 'I used a towel to stem the blood and washed my hands under the tap then I called the ambulance.' Hanghang, from Pingdingshan City, in the Henan province, told reporters at People's Daily Online that when the explosion happened he didn't dare tell his parents and called the ambulance service himself following the accident last week. He is now being treated in Ping Mei Group Hospital and is expected to need several operations to repair the damage. Hurt: Hanghang pictured lying in a hospital bed after a mobile phone exploded, injuring his face and hand . Doctors said he had 4cm injury to his face which exposed part of his lower jawbone as well as trauma to his left hand as well as lower legs and knees. He underwent emergency surgery before he was sent to the burns unit and onto the plastic surgery inpatient department. Experts believe there are three main reasons a phone may explode like this. The first is the battery itself is damaged and although it is connected to a charger it isn’t actually charging. A short circuit is another possible cause but this is a less likely unless the phone has been illegally modified in some way. The most common cause  is improper charging. It affects lithium batteries more where the phone may be fully charged but is left on charging or if phone is used whilst charging may lead to lithium batteries overheating. Overheating and poor contact can result in a sudden discharge of a current and cause an explosion. Tips include to avoid using the phone while the battery is being charged by disconnecting the phone from charger before connecting a call or using any of its functions. Ensure it is not over-charged by removing the electric supply when the battery is fully charged. If the battery seems to have swollen, it should be replaced immediately. Hanghang said he could not be sure of the type of phone as it was one of several old phones. He said: 'It was the battery that exploded. I have heard my classmates talk about this happening but I never thought it would happen to me.'
Hanghang was playing on the phone after waking up early for school .
He said the phone felt hot and then blew up in his hand .
It left his jawbone exposed and injuries to his hand, leg and knee .
Experts blame battery as most likely cause of blast .