The person who won this year's $1.3 billion Mega Millions lottery has yet to claim the jackpot nearly a month after the ticket was sold. 

The unknown individual bought the winning ticket at a Speedway gas station in Des Plaines, Illinois.

It marked the third-largest single winning in U.S. lottery history and the second-largest Mega Millions prize. Lottery officials said they're still waiting to hear from the winner.

"We don't know whether or not they even know that they won a prize," Harold Mays, director of Illinois' lottery, told The Guardian on Friday. "So, I encourage everybody to check your ticket."

Mega Millions winners have a year from the drawing date to claim their prize, according to lottery rules. Winners also have 60 days to choose whether they want the money in a lump sum or smaller annual payments. 

If the winner doesn't claim the prize, each state that participates in the Mega Millions lottery will get their portion returned, according to contest rules.

Mega Millions is played in 45 states as well as Washington, D.C., and the U.S. Virgin Islands. The game is coordinated by state lotteries.