Olympic swimming champion Michael Phelps was arrested and charged with DUI and other charges in Maryland early Tuesday morning.

Tuesday afternoon, Phelps pleaded for forgiveness on Twitter, writing, "I understand the severity of my actions and take full responsibility... I am deeply sorry."

Police say Phelps was clocked driving 84 mph in a 45 mph zone on southbound Interstate 395 leaving Baltimore.

An officer then followed Phelps' white 2014 Land Rover through the Fort McHenry Tunnel on northbound Interstate 95, said Maryland Transportation Authority Police.

Phelps was speeding and crossing double lines in the tunnel, they said.

The officer stopped Phelps just beyond the tunnel’s toll plaza. Authorities say he appeared to be under the influence and failed a series of field sobriety tests. Phelps was cooperative during the process, they said.

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Phelps was arrested around 1:40 a.m., TMZ first reported. He was charged with DUI, excessive speed and crossing double lane lines, and was later released.

The swimmer posted a series of tweets Tuesday afternoon, apologizing for the incident. "I understand the severity of my actions and take full responsibility," he said in part. "I know these words may not mean much right now but I am deeply sorry to everyone I have let down."

Phelps is the most decorated Olympic athlete in history with 22 medals: 18 gold, two silver and two bronze. He won an unprecedented eight gold medals in eight events at the Beijing Games in 2008, and returned to win four more golds at the London Games in 2012.

The swimmer said after the London Games that he was finished with competitive swimming. But he recently returned to the pool, competing in significant championship events this summer. He has not yet confirmed his plans for the Summer Games in Rio in 2016.

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Phelps has been charged with DUI previously. In November 2004, he was stopped by state troopers in Salisbury, Maryland, after failing to stop for a stop sign. He was 19 at the time.

In that case, Phelps pleaded guilty to driving while impaired. He was fined $250 and was ordered to serve 18 months probation.

During an interview with Matt Lauer on "Today," Phelps called the event an isolated incident and said he had "let myself down and my family down... I think I let a lot of people in the country down."

Phelps faced further controversy when a photograph surfaced in February 2009 showing him with a water pipe used to smoke tobacco or marijuana.

The O’Malleys' 18-year-old daughter Tara was hospitalized briefly last night in Baltimore after attending a graduation celebration.

Phelps publicly apologized and admitted that the image, taken at a student party at the University of South Carolina, was authentic. The brouhaha surrounding the photo resulted in the swimmer losing Kellogg's as a sponsor and a three-month suspension from USA Swimming.