Dell (DELL) - Get Report expanded last month's laptop battery recall program by 100,000 units.

The Round Rock, Texas, company said it received unexplained "additional information" about Sony battery packs linked to a possible risk of fire or explosion. Dell is now recalling 4.2 million Sony battery packs, up from the previous 4.1 million.

Apple

(AAPL) - Get Report

, Toshiba and Lenovo have also recalled Sony laptop battery packs after the devices were said to overheat in some cases and catch fire.