South Africa’s National Lotteries Commission (NLC) will be investigating an unusual national lottery draw which resulted in 20 jackpot winners.

The winning numbers in South Africa’s national lottery on December 1 have sparked accusations of fraud over their unusual sequence.

Tuesday’s PowerBall lottery saw the numbers five, six, seven, eight and nine drawn, while the Powerball itself was, unsurprisingly, 10.

Some South Africans have alleged a scam and an investigation is underway by the NLC, who said in a statement on Twitter: “This occurrence, while uncommon, is not impossible, with the odds of any set of numbers selected for PowerBall being 1 in 42 million.

“The NLC would like to assure all South Africans that all National Lottery games and methods used to conduct draws undergo a rigorous process of review prior to approval by the NLC.

“This is to ensure that the National Lottery is conducted with integrity and all players are afforded an equal chance of winning prizes.”

The NLC added that it had received a report on the unusual numbers from the lottery’s provider, Ithuba, and recommended that it “maintains an educational campaign… on the possibilities of winning combinations, the odds of winning and how the RNG works, in order to keep players knowledgeable and to maintain the integrity of the National Lottery.”

Ithuba tweeted: “Congratulations to tonight’s 20 winners of the PowerBall draw. These numbers may be unexpected, but we see many players opt to play these sequences.”

The organisers said 20 people purchased a winning ticket and won 5.7m rands ($370,000; £278,000) each. Another 79 ticket holders won 6,283 rands each for guessing the sequence from five up to nine but missing the PowerBall.

In March 2003, 33 players won a share of the jackpot, according to a South African website that tallies results.