CHARLOTTE, N.C. – Suspended NASCAR driver AJ 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.

“AJ 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. “AJ 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.”