NEW YORK -- A Wal-Mart worker died after a throng of unruly shoppers broke down the doors and trampled him moments after the Long Island store opened early Friday for day-after-Thanksgiving bargain hunting, police said.

Wal-Mart Stores Inc., in Bentonville, Ark., would not confirm the reports of a stampede at the Valley Stream outlet but said a "medical emergency" had caused them to close the store.

"Local authorities are looking into the situation," said Wal-Mart representative Dan Fogleman. "Until such time that they've completed their assessment it would be inappropriate for me to share any additional information."

The 34-year-old Wal-Mart worker was taken to a hospital, where he was pronounced dead at about 6 a.m., Nassau County police said. The exact cause of death had not been determined, and the man's name was not released.

A 28-year-old pregnant woman and three other shoppers suffered minor injuries and also were taken to hospitals for observation, said Nassau County police Lt. Michael Fleming of the Fifth Squad.

Police said the shoppers knocked the man to the ground at 5:03 a.m., three minutes after the store opened. It wasn't immediately clear how large the crowd was.

Shoppers around the country lined up early outside stores Friday in the annual bargain hunting ritual known as Black Friday. It got that name because it's historically been the day when stores broke into profitability for the full year.

Many stores open early and stay open late. The Valley Stream Wal-Mart usually opens at 9 a.m.

Nassau County police were at the scene investigating.