Lottery officials in the eastern US state of Maryland said on Monday that a winner had come forward to claim his or her share of the record $US656 million ($640 million) Mega Millions jackpot.
Maryland lottery director Stephen Martino was to hold a press conference in Baltimore on Tuesday "to provide details about the winning ticket", officials said.
A lottery spokeswoman told The Baltimore Sun that the winner - who purchased the ticket at a 7-Eleven convenience store in Baltimore County - wished to remain anonymous, but a "storyline" would be shared with the public.
A Haitian-born mother of seven, Mirlande Wilson, 37, who claimed last week that she held Maryland's winning Mega Millions ticket later told a Washington television station that she had "misplaced" it.
Two of the three winning tickets in the March 30 drawing have now been confirmed.
Kansas lottery chief Dennis Wilson said his state's winner turned up at his offices in Topeka on Friday with a lawyer and financial officer in tow - and a request to stay out of the headlines.
Tickets with the winning combination of 2, 4, 23, 38, 46 plus Mega Ball 23 were sold in Illinois, Kansas and Maryland amid an unprecedented nationwide lottery-buying frenzy.