Jan. 27, 2012 -- As the deadline to claim a $16 million Hot Lotto jackpot passed without a winner today, the Iowa attorney general's office launched a criminal investigation into the only person who tried to claim the prize.

"We wanted to pay the prize, we were more than prepared to pay the prize," lottery spokeswoman Mary Neubauer said. "But we didn't think it was a responsible thing to do."

The jackpot disappeared as the clocked ticked past 4 p.m. ET, reverting to the Iowa state treasury. And instead of a celebration, the state began an investigation.

"We opened a criminal investigation to learn more," said Geoff Greenwood, a spokesman for the attorney general's office. "We have some questions about the circumstances of this ticket, and we're trying to determine who purchased it and how it was presented."

Officials had set the deadline hoping to award the prize to the sole claimant, Crawford Shaw, a New York-based attorney who signed the winning ticket. But Shaw refused to disclose how he got the ticket or who his client was.

Iowa's $16 Million Hot Lotto Jackpot Goes Unclaimed

Shaw said that the ticket and winnings belonged to the Hexham Family Trust, but misspelled the name on the ticket, writing "Hexam." Shaw said he could not disclose who his client was and only confirmed that the trust he represented was based in Belize.

The investigation will try to determine how Shaw became the owner of the winning lottery ticket, purchased in Des Moines, Iowa, in December 2010. The lottery has obtained a surveillance video of the man who purchased the ticket at a Des Moines, Iowa, convenience store, but would not release details about the video.

Greenwood said the investigation will look into the surveillance video and ticket purchase.

Iowa Lottery officials drew the winning numbers for the jackpot in December 2010, but the prize went unclaimed for close to a year despite heavy advertising by the lottery for the winner to come forward. With two hours to go until the prize would be forfeited in December 2011, two Iowa attorneys presented the winning ticket, signed by Shaw, at the lottery headquarters.

They also did not provide any explanation of how Shaw obtained the ticket.

"These are not tough questions that we've been asking, just very basic factual information that we get from any prize winner. It is simply us doing our duty to make sure nothing was amiss," said Neubauer.

The lottery set a deadline of 4 p.m. today for Shaw and the attorneys to satisfactorily answer their questions. The attorneys contacted the lottery Thursday evening to confirm that Shaw was withdrawing his claim.

"I still don't know why it was so difficult for the information to be provided, but if that's the case, that's how it will end," Neubauer said.

The attorney general's office will work with the Iowa Division of Criminal Investigations to learn more about the winning ticket, Greenwood said.

The case is the second time in recent months that a lottery was claimed by a mysterious trust arranged by attorneys. In Connecticut in November, three bankers claimed a $254 million Powerball in the name of the Putnam Avenue Family Trust.

A friend of one of the bankers said they were a front for a fourth, anonymous winner, but the trustees denied that claim. They were awarded the prize money.

Neubauer, of the Iowa lottery, said that despite what happens in other lotteries around the country, Iowa state law requires that winners' names be public information, a statute that determined the outcome in Shaw's claim today.