Updated at 12:45 p.m. ET: LONDON - The winner of a lottery prize worth more than $100 million will lose the money if the ticket holder does not come forward in the next few days, organizers in the U.K. warned Wednesday.

Under lottery rules, the “truly amazing” and “staggering” prize will go to “good causes” supported by the U.K.’s National Lottery unless it is claimed by 11 p.m. local time (6 p.m. ET) on Wednesday next week, the organizers said in a statement.

“If you play EuroMillions and think you could have the winning ticket, check in the pockets of your clothing, in wallets, bags and down the back of the sofa – you could literally be sitting on a fortune!” it added.

The ticket for the EuroMillions lottery draw on June 8 was bought in the Stevenage and Hitchen area of England.

The hunt for the winner in the U.K. comes amid growing excitement in the U.S. about the Powerball jackpot, which is now worth $550 million.

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The winning numbers were 5, 11, 22, 34, 40 with the “lucky stars” 9 and 11.

A spokesman for Camelot, which runs the National Lottery, told NBC News that they were doing their best to publicize the existence of the unclaimed ticket.

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He said there was initially a publicity campaign in the Stevenage and Hitchen area, but this was now being expanded across the U.K.

The spokesman said they had also taken the campaign to nearby Luton Airport, which offers flights to 90 destinations worldwide, including South Africa, Thailand, Morocco, Spain, Israel, Iceland, India and China – but not the U.S. or Canada.

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He said the biggest lost prize in the lottery’s history was more than $14 million, but added that a $4 million prize had been claimed on the last day it was available in 2009.

“While there’s still time, there’s still hope,” he said.

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