Olympic swimmer Michael Phelps spent eight hours gambling at the Horseshoe Casino in Baltimore, Maryland before his Tuesday arrest for driving under the influence, according to a report. Phelps was allegedly traveling 84 mph, in a 45 mph zone, when he was pulled over by a Maryland Transportation Authority police officer.

Phelps, 29, arrived at the Horseshoe Casino at around 5 p.m. EDT Monday and spent the night playing blackjack and drinking beer in a private gambling room, sources told TMZ Sports. He didn't leave the casino until around 1 a.m. Tuesday.

The 18-time Olympic gold medalist was pulled over at around 1:40 a.m., mere miles away from the casino. He's a regular at the Horseshoe, where he played poker last month, TMZ Sports reported.

Though authorities initially stopped Phelps for speeding, the officers realized that he was drunk and subjected him to field sobriety tests. The swimmer was cooperative throughout the process, the MDTA said in a statement, via CBS Baltimore. His blood alcohol level was nearly twice the legal limit, sources told TMZ Sports.

Phelps was booked on charges of DUI, excessive speeding and crossing double-lane lines. He took to Twitter on Tuesday to apologize for his actions.

“Earlier this morning, I was arrested and charged with DUI, excessive speeding and crossing double lane lines,” Phelps said. “I understand the severity of my actions and take full responsibility. I know these words may not mean much right now but I am deeply sorry to everyone I have let down.”

It was Phelps’ second DUI arrest. He was arrested in 2004 at age 19 and charged with DUI, violation of license restriction and failure to obey a stop sign. He reached a plea deal and served 18 months' probation.