Two vehicles overturned in the accident on the A1 in East Lothian.
The crash took place only a few miles north of the spot where an accident claimed the lives of a West Lothian couple last week.
The latest incident happened shortly before 1100 BST on Tuesday at the Beltonford roundabout near Dunbar.
Firefighters from East Linton, Haddington and Dunbar used winching equipment to free those trapped in the wreckage after two of the vehicles overturned.
Two men and one woman in the minibus died in the accident.
Another two men, a woman and her infant child were injured.
They were taken to the Edinburgh Royal Infirmary with minor injuries.
A hospital spokeswoman said all four were later discharged after receiving treatment.
The hospital's Medic One flying squad and four ambulances were called to the scene.
The road was closed for several hours as crash investigators probed the cause of the accident.
Lengthy tailbacks were reported after the road reopened on Tuesday afternoon.
A spokesman for Lothian and Borders Fire Brigade said: "I would certainly say this ranks among the worst accidents we've ever had to deal with on the A1."
Several injured
Last Friday, two people died after an accident on the same road near Torness Power Station.
James Jenkinson, 53, and Andrea Jenkinson, 51, were both from Whitburn in West Lothian.
Several other people, including a schoolboy, were injured in the accident, which involved two cars.
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