LITTLE ROCK, Ark. — Wal-Mart Stores said Wednesday it will keep its stores open 24 hours and take new crowd-control measures Thanksgiving weekend after a temporary employee was trampled to death in a Black Friday rush last year.

The world’s largest retailer says day-after-Thanksgiving sales will begin at 5 a.m. Nov. 27, but most U.S. stores will be open 24 hours to prevent a mad dash. The announcement doesn’t affect most of Wal-Mart’s Supercenters, which are already open 24 hours. Spokesman David Tovar said the change affects about 800 stores that aren’t currently open round-the-clock.