Former junior welterweight titlist Kendall Holt's postfight drug test following his knockout loss last month to titleholder Lamont Peterson came back with an "atypical finding" for human chorionic gonadotropin, the banned substance commonly known as hCG, the promoters for both fighters told ESPN.com on Thursday.

In his hometown of Washington, D.C., Peterson knocked out Holt in the eighth round to retain his 140-pound world title on Feb. 22 in the main event of ESPN2's "Friday Night Fights."

HCG is the same substance for which baseball player Manny Ramirez tested positive, leading to a 50-game suspension by Major League Baseball in 2009. It is a female fertility drug often used by steroid users to restart natural testosterone production. It also has been used to assist in weight loss. Its presence in the body also can be an indicator of cancer.

On Thursday, the results of the Washington D.C. Boxing and Wrestling Commission tests were forwarded to the IBF, whose title was at stake, and the IBF then shared them with Gary Shaw, Holt's promoter, and Richard Schaefer of Golden Boy Promotions, Peterson's promoter.

When the test results were initially released, the IBF and the promoters were unsure which fighter had the questionable test because the fighters are identified only by a lab control number.

Later in the day, however, Shaw said the number assigned to Holt produced the bad test.

"It could be one of two things -- either he took something or it could be showing something else is wrong, like cancer," Shaw said. "They're going to do more testing on the sample. Kendall spoke to John [Beninati], my matchmaker, and told him he only took fish oil. Sounds like a fish story to me.

"I have the documents from the IBF, and I am aware that the atypical sample has the control number that was assigned to Kendall Holt and that he signed for."

Schaefer also said the IBF had informed him that it was Holt's test that was "atypical."

Daryl Peoples, president of the IBF, said Holt would have the opportunity to have his "B" sample tested.

Ring magazine's website erroneously reported earlier Thursday that it was Peterson whose sample was positive for hCG, a more serious accusation than it would be for most fighters. That is because when Peterson faced Holt, it was his first fight in 14 months, a layoff caused by his testing positive for the banned substance synthetic testosterone last spring, just a week before his rematch with former titleholder Amir Khan, which was subsequently canceled.

Also, Holt's attorney, Pat English, sent a strongly worded letter to Peoples, a copy of which was obtained by ESPN.com, in which he stated, with no particular proof, that it was Peterson's test that was positive.

Peterson is now training for a title defense against interim titlist Lucas Matthysse of Argentina. They are due to meet May 18 in the main event of a Showtime card at Boardwalk Hall in Atlantic City, N.J.