However, the firm would not confirm that this was their conclusion.
“We understand the need for answers and appreciate your continued patience as well as that of our valued customers, partners and stakeholders,” it said in a statement.
“We are working diligently to ensure that we have a comprehensive update and will provide more information in the coming weeks once we have the final report.”
Battery technology has been slower to evolve than the many battery-powered devices that rely on it, said Ian Fogg, senior analyst at IHS,
“There is enormous pressure to improve battery tech. It’s one of the areas that’s holding back mobile devices and a range of other products,” he told the BBC.
“Manufacturers have been balancing out consumer demand for longer-lived batteries, and more powerful devices with better graphics and larger more detailed displays, with the sophistication of battery tech.
“It’s very difficult to push up the capacity of batteries and there is always a risk that a battery in any device could fail.”