AJ Allmendinger's positive NASCAR drug test was due to a "stimulant," his business manager said in a statement on Wednesday afternoon. The specific stimulant was not named.

Tara Ragan said Allmendinger has "no idea why the first test was positive and he has never knowingly taken any prohibited substance."

"AJ is collecting his medicines and supplements for testing to determine whether an over the counter product caused his positive test," Ragan said. "AJ and all of us at Walldinger Racing respect NASCAR's testing program, and he has requested that his 'B' sample be tested as part of the process of getting to the bottom of this."

Allmendinger's 'A' sample was tested and it was determined the stimulant was "slightly above the threshold" allowed by NASCAR, Ragan said.

As of Wednesday morning, Ragan said the 'B' sample had not been tested and the driver had not been informed of when that testing would take place. Allmendinger can review the scientific data once the 'B' sample has been tested, she said.

"Thanks again for all of the support of our fans, team, and sponsors as we continue working through the process," Ragan said.