AJ Allmendinger has been placed on indefinite suspension from all NASCAR competition, after the 'B' drugs test sample that he gave NASCAR Sprint Cup officials at Kentucky in June has also tested positive for an illegal substance under NASCAR's substance abuse policy.

That means that Allmendinger's suspension will now last until such time that he completes a mandatory 'road to recovery' program and can convince the sport's medical officers that he is fit to return to driving.

Allmendinger was placed on temporary suspension on July 8 after the initial 'A' sample tested positive for what Allmendinger's management team later revealed was a 'stimulant', defined in NASCAR's drug policy as "amphetamine, methamphetamine, Ecstasy (MDMA), Eve (MDEA), MDA, PMA, Phentermine, and other amphetamine derivatives and related compounds."

NASCAR's rules allowed Allmendinger to ask for the second urine sample given at the same time as the first to be tested, with a toxicologist of Allmendinger's choosing allowed to be present. That was scheduled to start at 8.30am on July 24.

Aegis Analytical Laboratories in Nashville subsequently delivered the results of the 'B' sample test on Tuesday evening, which confirmed the positive findings of the first. Allmendinger's suspension was then duly made official and indefinite.

"AJ Allmendinger, driver of the #22 car in the NASCAR Sprint Cup Series, has been suspended indefinitely from NASCAR for violating the sanctioning body's substance abuse policy," read the brief official announcement from the sanctioning body. "Allmendinger was found to have violated Sections 12-1 (actions detrimental to stock car racing) and 19 (NASCAR's substance abuse policy) of the 2012 NASCAR rule book."

The statement added: "As outlined in the rule book, NASCAR next will provide Allmendinger a letter outlining a process for reinstatement. By agreeing to the letter, he will be allowed to participate in the Road to Recovery Program."

Allmendinger's representatives said that they were disappointed with the latest positive result, and strongly denied that the driver had intentionally or knowingly violated the substance abuse policy.

"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, the vice president of Walldinger Racing Inc. "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.

"We continue to be extremely grateful by the breadth and scope of support for AJ from his fans and partners," the statement continued. "We would like to again thank NASCAR, Penske Racing and all our sponsor partners for the open communication, and for helping us at every step in this process."

As for the future: "We are working closely with NASCAR and Penske Racing to identify the next action steps in this process," Regan said. "We expect to have further updates in the upcoming days."

The 30-year-old driver with 169 Cup series starts under his belt since switching from Champ Car World Series open wheel racing in 2006. He left Richard Petty Motorsports at the end of 2011 to the up a one-year contract with Penske Racing to replace Kurt Busch in the high profile #22 Shell/Pennzoil car, and has enjoyed his best run of form of his Cup career in the first half of the 2012 season.

Asked on a radio interview how Allmendinger had taken the news, Ragan said "Not well," adding: "Everybody who knows AJ, this is his life ... All that he's done is race cars and racing. Everything that he does just about every single day is geared toward that."

Allmendinger himself posted updates on social media network Twitter following the announcement: "I'm sorry we even have to have this going on. But I promise I will do whatever it takes to get to the bottom of this and get back out there no matter what," he tweeted. "I just want to say thank you first and foremost for all of u sticking by me."

Allmendinger's Sprint Cup team, Penske Racing, also issued a statement followed the confirmation of the 'B' test findings at 9pm local time on Tuesday.

"Penske Racing is very disappointed with the result of the B sample test and will evaluate its course of action as it pertains to AJ over the coming week," it read, confirming that "Penske Racing was notified today of AJ Allmendinger's positive B sample test. We respect NASCAR's policy and the process they have taken with this matter."

The team also announced that Sam Hornish Jr. will now continue behind the wheel of the #22 Penske Dodge for the immediate future, confirming that he would be racing at Indianapolis this weekend and at Pocono at the start of August.

The primary sponsor of the #22, Shell Oil Company, also released a statement about the outcome of the drugs testing process.

"Shell and Pennzoil believe that the process and procedures that NASCAR has in place as part of their substance abuse policy are appropriate and serve to ensure that the sport and its participants are held to the highest standards," the statement read. "We share Penske Racing's disappointment with the result of AJ's B sample test and will work closely with them to determine plans moving forward. We hope for the best for AJ during this difficult time."

NASCAR itself has not disclosed any details about the type of drug identified in Allmendinger's blood test, the level of drug found in a driver's system, or indicated what sort of treatment programme the driver must now undertake or how likely that will sideline him from the sport.

"As far as NASCAR is concerned it's still a full-stop violation," said NASCAR spokesman David Higdon. "If someone tests positive, it's a violation ... We choose not to disclose the level as it does not factor into the decision. If you're positive, you're positive."

Five Cup drivers are tested at random at each race weekend. Crew personnel and NASCAR officials are also tested under the series' substance abuse policy. Some crew personnel who have failed drugs tests have gone on to complete their treatment program and return to the sport, but no driver in any of the three national race series who has failed a drugs test has subsequently been able to return to competition.

The most notorious case was that of Jeremy Mayfield, the only other Sprint Cup driver to have failed a drugs test since the current random testing was introduced in 2009. Mayfield was suspended three years ago after a positive test for methamphetamines and who subsequently filed a lawsuit against NASCAR that ultimately proved unsuccessful and was dropped earlier this year. Mayfield himself never completed his mandatory 'road to recovery' and is still on suspension; he's also been charged with a variety of criminal offences on separate matters following a police raid on this home at the end of 2011.