The China Consumers Association has asked Apple to investigate "a considerable number" of reports by users of iPhone 6 and 6s phones that the devices have been shutting off and cannot be turned back on again, it said on Tuesday.

The reported problems specifically involve users seeing their iPhones automatically shut off despite 50-60 percent battery levels, and the involuntary shutting off in room temperature or colder environments, as well as the inability to turn the cellphone back on despite continuous battery charging, the statement said.

"In view that Apple iPhone 6 and iPhone 6s series cellphones in China have a considerable number of users, and the number of people who've reported this problem is rather many, China Consumer Association has already made a query with Apple," the association said in a statement on its website.

Apple did not respond to a request for comment when contacted outside regular hours on Tuesday. 

Source: NBCNews