DES MOINES, Iowa — A newly unsealed memo shows the Iowa Lottery kept marketing four popular games despite an August 2015 warning from its security chief that their integrity was compromised.

The memo was written following the trial of Eddie Tipton, who was convicted of rigging a Hot Lotto jackpot worth $16 million.

Steve Bogle, its vice president of security, recommended that the lottery immediately suspend sales of Hot Lotto, Pick 3, Pick 4, and All or Nothing. He told CEO Terry Rich, "we cannot allow the citizens of Iowa to continue playing these games."

Bogle's recommendation followed an independent audit of the Multi-State Lottery Association, which ran the games using random number generators.

Less than two months after the warning, Lottery Post reported that Tipton had been rigging multiple lottery games that used MUSL's computerized drawing system for years. (See HOT LOTTO DRAWING CHEAT CHARGED WITH RIGGING MORE JACKPOTS, Lottery Post, Oct. 9, 2015.)

The audit remains secret. But Bogle's memo says it identified a lack of security protocols and oversight that undermined their integrity.

A lottery spokeswoman says Rich rejected Bogle's recommendation after speaking with the audit's author, who said there were potential vulnerabilities but no evidence of ongoing manipulation.

The memo became public after a judge granted The Des Moines Register's request for its release in an ongoing lawsuit.

Timeline of the biggest crime in US lottery history

The following is a compilation of Lottery Post news coverage chronicling the Hot Lotto mystery and subsequently discovered crime.

We start the timeline with a news story indicating that only 3 months remained for the $16 million Hot Lotto jackpot to be claimed.