NASCAR suspended Sprint Cup Series driver A.J. Allmendinger indefinitely on Tuesday after a test of his backup urine sample confirmed the original positive result.

The violation of NASCAR’s substance abuse policy puts Allmendinger’s future in NASCAR and at Penske Racing in doubt.

Allmendinger originally was suspended on July 7 after failing a random drug test taken in late June.

His backup “B” urine sample was tested on Tuesday and NASCAR officials announced the result and subsequent suspension later that night.

Officials did not announce what substance Allmendinger tested positive for.

Allmendinger previously said he tested positive for a stimulant, but did not give specifics. He has denied knowingly taking a banned substance.

“This was not the news we wanted to hear and we will work to get to the source of what may have caused this,” said Tara Ragan, Allmendinger’s business manager, in a statement.

“To that end, we have secured the services of an independent lab to conduct thorough testing on every product within AJ’s home and motor coach to find what might collaborate with his test, which created results that were within nanograms of accepted standards.”