CHARLOTTE, N.C. – Suspended NASCAR driver A.J. Allmendinger said Wednesday that he tested positive for a stimulant, and was collecting his medicines and supplements in an attempt to figure out what got him in trouble.

A statement issued by Allmendinger’s business manager did not identify the stimulant and said the driver does not know what caused him to fail the random test conducted June 29. He was suspended Saturday and NASCAR has not revealed the substance, either.

“A.J. tested positive for a stimulant. He has no idea why the first test was positive, and he has never knowingly taken any prohibited substance,” said Tara Ragan, vice president of Allmendinger’s Walldinger Racing Inc. “A.J. is collecting his medicines and supplements for testing to determine whether an over-the-counter product caused his positive test.”

Allmendinger is the second Sprint Cup Series driver to be suspended under the NASCAR drug policy implemented in 2009. The 30-year-old Allmendinger has requested his “B” urine sample be tested, and it’s not clear when that will occur.

Allmendinger said Tuesday that he would never knowingly take a prohibited substance.

“Obviously I would never do anything to jeopardize my opportunity here at Penske Racing or to my fellow drivers. I am very conscious about my training and health, and would never knowingly take a prohibited drug,” he said.

According to NASCAR’s drug policy, a stimulant is defined as “amphetamine, methamphetamine, Ecstasy (MDMA), Eve (MDEA), MDA, PMA, Phentermine, and other amphetamine derivatives and related compounds.”

In March, Allmendinger signed on as a brand ambassador for “Fuel in a Bottle,” energy and protein power shots owned by Charlotte-based BYB Brands.

There’s been no official link to his positive test and the power shots. The March press release announcing the partnership with Allmendinger described “Fuel in a Bottle” as a booster that “provides a quick energy boost in convenient 2-ounce liquid form. It is packed with B vitamins, is sugar free and has zero calories.”

The power boost includes “essential amino acids that your body needs,” the release said. “Both varieties of Fuel in a Bottle allow consumers to recharge in minutes. Run stronger for hours.”

Among the ingredients listed on the label are L-Phenylalanine and caffeine, which are both mild stimulants.

Jeremy Mayfield, the first driver to be suspended under the policy, tested positive for methamphetamine. He has denied for more than three years that he ever took meth, and blamed the positive test on a mix of an over-the-counter allergy remedy and a prescription for attention deficit disorder.

Rather than go through NASCAR’s recovery program, Mayfield fought in court to have his suspension overturned. He abandoned his bid this year.

The suspension was announced hours before Saturday night’s race at Daytona International Speedway and Sam Hornish Jr. was hustled in to race in Allmendinger’s place. Penske Racing has already said that Hornish will drive the No. 22 Dodge this weekend at New Hampshire.

FORMULA 1: Mark Webber has ended another summer of speculation about his future with Red Bull. Now he can only hope the focus is on hunting down Fernando Alonso in the Formula One title race.

Small chance of that.

Signing up for another year with Red Bull ensures another chapter in the intriguing duel with Sebastian Vettel for team superiority.

Webber openly concedes all of this can be “stressful” to grapple with as motor sport remains on alert for the next bout of squabbling between the pair.

“It’s not easy for both of us to be at the front and I can understand that as both of us are thinking about ourselves sometimes,” Webber said. “But ultimately we know that we need to get the cars home and get the best results for us and the team.”

Vettel is the reigning double world champion, but a third title isn’t looking certain.

Webber notched a second victory this season on Sunday by overtaking Alonso with four laps remaining to win the British Grand Prix, leaving Vettel with just one win in 2012.

And while Webber is only 13 points behind Alonso, Vettel is 16 points adrift of his teammate in the drivers’ standings in third place.