Customers and staff at the Wal-Mart superstore in New Jersey were shocked after a man used the public address system to tell "all black people" to leave.
On Sunday evening at the Washington Township store, a male voice calmly announced: "Attention Wal-Mart customers: All black people leave the store now."
Officials from Wal-Mart Stores are reviewing security tapes to try to determine who made the announcement.
Witnesses told the Courier-Post newspaper that customers and store employees looked stunned.
Management later apologised.
Company spokeswoman Ashley Hardie says the incident was "unacceptable."
The retailer is looking to prevent it from happening in the future.
Washington Township police and the Gloucester County Prosecutor's Office also are investigating.
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