A 13-year-old schoolgirl in the US state of Maine was released from hospital on Friday after she was treated for burns caused by her iPhone setting alight in her trouser pocket.

When the Year 8 girl sat down during her first class of the day at Middle School of the Kennebunks (MSK), she heard a pop in her back pocket where she was keeping her smartphone, Bangor Daily News reported.

Smoke then began to rise out of her trousers and the girl’s friends asked the boys in the classroom to step outside so she could remove her trousers, while teachers got her a blanket. She was later praised by the school’s Principal for remembering to immediately “strop, drop, and roll”.

When the iPhone fell out of her pocket during this process it was “visibly burnt” according to MSK's Principal Jeff Rodman.

Emergency services quickly arrived, and she was taken to Southern Maine Health Care Centre. She was released later that day after she received treatment for what paramedics called “moderate” burns.

The Principal emailed parents to notify them of the incident on Friday morning, and said that the student was helped immediately by both her classmates and the school staff.

The fire marshal in Kennebunk, in York County, is investigating the incident.

Emergency Medical Services Division Chief for Kennebunk, Andrew Palmeri, told the newspaper it appears as though the phone’s battery “shorted out.”

“People should obviously use caution when placing their phones in their back pockets so as not to crush them and cause an electrical short,” he said.

According to the crew, the student’s quick thinking, as well as that of those around her, prevented any worse burns or injury.

Apple is yet to respond to a request for a comment.