Updated January 31, 2018 12:01:15

Photo: The US Department of Justice and Securities and Exchange Commission are investigating Apple. (Reuters: David Gray)

US authorities are investigating Apple's slowing of older iPhones, according to published reports.

The Wall Street Journal and Bloomberg reported the Department of Justice and the Securities and Exchange Commission were probing whether Apple violated securities laws.

In December, the company admitted it may slow the smartphone's processor in the iPhone 6, iPhone 6s and iPhone SE when the battery was wearing out.

Apple apologised for the slowdown after a blogger's tests revealed the secretive practice.

It's a conspiracy theory as old as the iPhone, but Apple now confirms it does tinker with old iPhone models. But only to make the ageing smartphones run smoother.

Apple was previously rebuked by politicians, and faced a French probe and a slew of lawsuits that alleged the company aimed to increase sales of newer models.

Apple shares fell 0.6 per cent to close at US$166.97 and were down 7 per cent since Thursday.

Wall Street was also worried about weak demand for its flagship iPhone X.

The Justice Department and SEC declined to comment.

Apple did not respond to a request for comment.

ABC/AP

Topics: computers-and-technology, mobile-phones, information-and-communication, consumer-protection, united-states

First posted January 31, 2018 11:55:41