IBF and WBA junior welterweight titleholder Lamont Peterson has tested positive for a banned substance, which jeopardizes his May 19 rematch against Amir Khan that is slated for the Mandalay Bay Hotel in Las Vegas.

Peterson (30-1-1, 15 knockouts) and Khan (26-2, 18 KOs) contractually agreed to be randomly drug tested for blood and urine for their return bout by the Voluntary Anti-Doping Association (VADA) in advance of their HBO-televised clash.

In a letter to Nevada State Athletic Commission Executive Director Keith Kizer and obtained by RingTV.com, VADA President and founder, Margaret Goodman, wrote that a “urine specimen…was collected on March 19,” and that its test results were “consistent with the administration of an anabolic steroid such as testosterone.”

Peterson’s publicist, Andre Johnson, issued a statement to RingTV.com on behalf of the fighter and his manager, Barry Hunter, on Monday evening acknowledging the positive test but could not specify what the substance was.

This is the statement:

“We have tremendous respect for VADA and its mission. Lamont, Barry and the entire team emphatically support random drug testing in the most comprehensive manner possible. We are working expeditiously with a team of pathologists and other medical specialists to confirm the origin of the test result and in full compliance with the rules of the Nevada State Athletic Commission.

“Lamont has never had a positive test either before or after this isolated occurrence, and we plan to submit medical findings by close of business Tuesday reflecting the actual facts in support of Lamont’s good faith intentions and the requirements of the commission.”

RingTV.com was unable to reach Golden Boy Promotions CEO Richard Schaefer, who handles Khan, for comment.

Goodman wrote in an e-mail: “At this point in the process, it would be inappropriate for me to discuss this with the media.”

But Kizer told RingTV.com that he was informed of the positive test by Goodman. Kizer said that he then informed HBO, Schaefer, IBF and WBA officials as well as the Mandalay Bay Hotel of the situation.

“The Nevada Athletic Commission found out about it today, and I informed those groups,” said Kizer. “I confirmed it with Dr. Goodman and I let them know. They were all in the dark.”

A new operation, VADA debuted its testing with this past Saturday’s WBC junior middleweight title bout involving Saul Alvarez, who successfully defended his belt by a unanimous decision over former champ Sugar Shane Mosley.

Peterson took the belts from Khan by a split decision in December in Peterson’s native Washington, D.C.

Lem Satterfield can be reached at [email protected]