Lotto players claimed they spotted a fix in Saturday night's £4.5million TV draw after a ball appeared to have two different numbers on it.
Stunned viewers were perplexed when they thought the say the red number 38 ball also having a number 33 printed on it.
When the ball was revealed during Ireland's Lotto Plus 1 draw on Saturday evening, viewers were quick to spot it and questioned whether it was a "fix", the MailOnline reported.
But organisers today dismissed the claims and simply said it was an "illusion" caused by a "brief reflection of light".
Live footage on RTE showed the ball roll into its slot after being drawn as the second number.
When it came into shot, viewers were able to see the number 38 printed on the ball several times.
But they were left perplexed after seeing what they believed was a number 33 in the middle of the ball.
The 38 ball was drawn along with 1, 4, 29, 45, 46 and the bonus ball, 26.
Concerned players took to social media after being convinced they saw two different numbers on the ball.
David Connolly, from Dublin, uploaded a photograph on Twitter and suggested it could be a "fix".
He wrote: "Fixed Irish lotto, look at 33 & 38 on the same ball??"
Another social media user wrote: "Fixed Irish lotto, look at 33 & 38 on the same ball??"
Another person said: "How are chances in the Lotto fair when you put two different numbers on one ball what kind of stunt is this?"
A spokeswoman for the Irish National Lottery said the "illusion" was caused by a 'brief reflection of light'.
She said: "The National Lottery would like to assure its players of the integrity of Saturday night's Lotto Plus 1 draw.
"A brief reflection of light during filming caused an illusion and some players to think there were two numbers on ball 38.
"This was not the case. The weight and size of all Lotto balls, and the numbers, are strictly checked in advance of each draw.
"This process, as well as the draw itself, is independently observed by our auditors KPMG."