Four relatives of well-known British actress Helena Bonham Carter have reportedly been killed in a road accident in Limpopo, the Sunday Independent reported at the weekend.

According to Thabazimbi police, the accident happened at about 4pm on Wednesday on a dirt road between the Marakele game reserve and Thabazimbi, killing four people instantly.

They were 14-year-old Eton schoolboy Marcus Egerton-Warburton; his 74-year-old grandmother, Brenda Bonham Carter; his step-grandfather, 75-year-old Francis Kirkwood; and his aunt, 54-year-old Kay Boardman, Graham Bonham Carter's wife of a year.

Two more relatives were injured and were being treated at the Sunninghill hospital in Sandton.

According to the report, the minibus the family was travelling in had overturned due to a burst tyre, causing the driver to lose control of the vehicle the family had hired. The exact cause of the accident is, however, being investigated.

The actress, known for her roles in 'Harry Potter and the Order of the Phoenix', 'A Room with a View', 'Charlie and the Chocolate Factory', 'Corpse Bride' and 'Sweeney Todd: the Demon Barber of Fleet Street', has reportedly gone into mourning following news of the deaths, said the Sunday Independent report.