LAS VEGAS (AP) – Former WBC super welterweight champion Ricardo Mayorga tested positive for a banned substance after losing his title Saturday to Oscar De La Hoya.

Mayorga could be fined by the Nevada Athletic Commission after traces of the diuretic Furosemide, also known as Lasix, were found in his system, commission lawyer Keith Kizer said Thursday.

Kizer said boxing regulators notified Mayorga of the violation Wednesday. The Nicaraguan boxer has 20 days to respond before the commission decides whether to hold a hearing on the matter.

Mayorga’s Miami-based lawyer, Tony Gonzalez, did not immediately respond to a call seeking comment.

Another Nicaraguan boxer, Rosendo Alvarez, tested positive for the same substance last month. The Nevada Athletic Commisison suspended Alvarez’ license until the end of the year and he was fined $2,000.

“We’re thinking there must be a trainer or physician in Nicaragua that is recommending this for boxers,” said Alan Hopper, a spokesman for Don King Promotions, which represents Mayorga.

Diuretics are taken to lose weight quickly or to mask steriod use, Kizer said. Mayorga weighed in for the Saturday fight at 1531/2 pounds, or 41/2 pounds lighter than his fighting weight in October 2002 against Felix Trinidad.

Mark Taffet, senior vice president of HBO Sports, said Wednesday that De La Hoya’s technical knockout victory at the MGM Grand Arena sold 875,000 subscriptions and generated $43.8 million in pay-per-view revenue.

Mayorga earned a guarantee of $2 million and a share of each pay-per-view sale above 600,000.

AP-ES-05-11-06 1858EDT