Apple sank 3 per cent after the company pulled a software update for its iPhones late Wednesday as users complained that they weren't able to make calls.
The Dow was down 208 points, or 1.2 per cent, to 17,002 as of 10:50 a.m. Eastern time Thursday. The plunged wiped out the Dow's gain of 154 points the day before.
The Standard & Poor's 500 index fell 25 points, or 1.3 per cent, to 1,972.
The Nasdaq composite, which is heavily weighted with technology stocks, fell 78 points, or 1.7 per cent, to 4,477.