The chance of the same numbers appearing were one in four million
The Bulgarian authorities have ordered an investigation after the same six numbers were drawn in two consecutive rounds of the national lottery.
The numbers - 4, 15, 23, 24, 35 and 42 - were chosen by a machine live on television on 6 and 10 September.
An official of the Bulgarian lottery said manipulation was impossible.
A mathematician said the chance of the same six numbers coming up twice in a row was one in four million. But he said coincidences did happen.
Minister of Physical Education and Sport Svilen Neykov said the commission established to investigate would provide answers towards the end of the week.
The lottery organisers described it as a freak coincidence and pointed out that the numbers were drawn in a different order.
Nobody won the top prize in the first draw.
But a record 18 people guessed all six numbers in the 10 September draw.
Each will win 10,164 leva (£4,700).