Orange County Sheriff's deputies spotted Gore's blue Toyota Prius going more than 100 miles per hour (160 kph) on the I-5, the main north-south highway on the west coast, early Wednesday, police said.

When they pulled him over, police smelled marijuana, searched the car and allegedly found more of the drug, as well as vicodin, valium, xantax, and adderal, which is used to treat attention deficit disorder.

"He did not have prescriptions for any of these medications," sheriff's department spokesman Jim Amormino told AFP.

Gore was arrested and is being held on 20,000 dollar bail.

"He is still in custody," Amormino said.

Gore, 24, lives in Los Angeles and told authorities he was headed south to San Diego, Amormino said.

The arrest comes just days before Al Gore senior is due to join a series of concerts to raise awareness of global warming, "Live Earth."

The younger Gore has a history of drug and driving violations.

In 2003, the younger Gore was charged with marijuana possession in Maryland after police stopped the car he was driving for not having its headlights on. In February 2004 he entered a substance abuse program as part of a plea agreement.

Gore was charged with reckless driving in North Carolina in 2000 for allegedly driving 94 mph, and in September 2002, military police arrested him on suspicion of drunk driving near a military base in Virginia.

Gore graduated from Harvard in 2005.

His father has spoken widely about how, in April 1989, the younger Gore nearly died in a car accident in Maryland.

In Chicago, the former vice president made a book tour stop that -- though officially he is not in the 2008 presidential race -- had many trappings of the typical campaign appearance.

"I'm not planning to be a candidate again," Gore said, after a six-minute, campaign-style speech that touched on everything from his trademark issue of global warming to the Iraq war.

Supporters in the bookstore chanted to their Democratic favorite "run, Al, run."

Though he so far is not in the race, polls have shown that Gore, bested by President George W. Bush in 2000, is not too far behind Democratic presidential hopefuls Hillary Clinton and Barack Obama, with about 15 percent support of those polled.

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