Apple has cited "external factors" as the likely cause of iPhone 6 battery fires detailed in a Chinese consumer protection report that has gained publicity across the world.
The Shanghai Consumer Council released a report on Friday detailing battery fires in eight iPhone 6 handsets. It also detailed iPhone 6 handsets powering down before their batteries are depleted, which it attributed to a component's exposure to ambient air.
"The units we've analysed so far have clearly shown that external physical damage happened to them which led to the thermal event," an Apple spokesperson said.
She also said Apple was widening its investigation into the power-down issue.
The US tech firm has seen Chinese sales fall over the past three quarters as domestic smartphone makers compete with high-spec handsets at low price points. It is hoping to bounce back in the first quarter of next year with its iPhone 7.
But domestic handset makers also likely received a boost after South Korea's Samsung recalled 2.5 million Note 7 handsets globally following a series of battery fires, raising distrust of foreign smartphone brands, according to users, analysts and consumer groups.
The Shanghai Consumer Council in its report said that during Samsung's recall in October-November, complaints involving Apple products jumped, accounting for almost half the year-to-date total of 2763 - itself a nearly two-fold increase from 2015.
"The Samsung case did make [Chinese smartphone users] start to think an international brand doesn't necessarily equal a safe product," said Nicole Peng, Asia-Pacific director at researcher Canalys.