AJ Allmendinger has been suspended indefinitely after a second sample from a drug test collected earlier this month violated the league's substance abuse policy, according to NASCAR.

The driver of the No. 22 car at Penske Racing will next receive a letter from NASCAR outlining the terms and conditions of potential reinstatement. If Allmendinger chooses to participate, the following step would be further medical examination or treatment, according to NASCAR's Road to Recovery program.

NASCAR did not reveal the substance for which Allmendinger tested positive, citing the privacy of the individual involved. The testing of the "B" sample was conducted Tuesday at Aegis Sciences Corp. in Nashville, Tenn., which administers NASCAR's substance-abuse program. Allmendinger had a toxicologist of his own present for the test.

"This was not the news we wanted to hear and we will work to get to the source of what may have caused this," Tara Ragan, Allmendinger's business manager said 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. We are working closely with NASCAR and Penske Racing to identify the next action steps in this process. We continue to be extremely grateful by the breadth and scope of support for AJ from his fans and partners. 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. We expect to have further updates in the upcoming days."

Sam Hornish Jr. will continue to drive the No. 22 while Allmendinger is suspended.

"We respect NASCAR's policy and the process they have taken with this matter," the Penske team said in a statement. "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. Sam Hornish Jr., will drive the No. 22 Dodge Charger this weekend at Indianapolis and next weekend at Pocono."

NASCAR announced July 7 that Allmendinger's "A" sample from a random drug test conducted the previous weekend at Kentucky had violated the substance-abuse policy, and the driver had been suspended temporarily. Hornish, a regular competitor for Penske in the Nationwide Series, was flown back from Charlotte to race in that night's event at Daytona International Speedway, and also competed last week at New Hampshire in Allmendinger's usual No. 22 car.

On July 11, Ragan released a statement saying the driver had tested positive for a "stimulant." She added that Allmendinger was uncertain as to what could have led to the positive test, and that he was attempting to determine if it could have been inadvertently triggered by his consumption of an over-the-counter product.