The winning ticket for the National Lottery was bought in the area for the draw on May 12 and matched the six jackpot winning numbers, which were 1, 5, 18, 21, 23 and 33.
The total prize stands at £3,634,865 and organiser Camelot is urging players who were in the area two weeks ago to check their tickets.
A spokesman said: "This jackpot could really make a huge difference to somebody's life.
"We are urging everyone to check their old tickets again or look anywhere a missing ticket could be hiding.
"We have the champagne on ice and our fingers crossed the lucky winner comes forward to claim their win."
Anyone who believes they have the winning ticket can call 0845 9100000 to check their prize.
If no-one comes forward with the winning ticket before the claim deadline of November 8 then the prize money, plus all the interest it has generated, will go to charity.
More than 2800 people have become millionaires and £28billion has been raised for charity through ticket sales since the Lottery launched in November 1994, says Camelot.