Lineal middleweight champion Sergio Martinez and titleholder Julio Cesar Chavez Jr., who both submitted to random urine tests conducted by the Nevada State Athletic Commission on July 11, had their drug tests come back negative on Thursday, according to commission executive director Keith Kizer.

In one of the year's biggest fights, Martinez and Chavez are to meet on Sept. 15 (HBO PPV) at the Thomas & Mack Center in Las Vegas.

Nevada does not randomly test fighters for every fight, but reserves the right to ask for what it calls random "in-training" tests from any fighter -- boxing or MMA -- who is licensed by the state. Kizer said he or any of the five commissioners can ask for a fighter to be randomly tested and, in the case of Martinez and Chavez, commissioner Francisco Aguilar asked for the tests to be performed.

The Nevada commission has done it for other major fights, Kizer said, including for Floyd Mayweather Jr.-Miguel Cotto, Mayweather-Victor Ortiz and Abner Mares-Joseph Agbeko I.

"I found out that (Martinez and Chavez) would be here for a press conference, so we got their samples that day," Kizer said.

Kizer said Martinez and Chavez, who were at the Wynn Resort (the host casino for the fight) for a news conference, had about two hours' notice before their sample was collected. Kizer said that was not enough time to get rid of anything illegal that may have been in their systems.

Kizer said the fighters are subject to further random tests leading up to the fight. In addition, both will have to provide urine samples on fight night -- both before and after the bout -- which is the norm in Nevada for title fights.

Although the Nevada commission gave no specific reason for selecting Chavez and Martinez to be tested, Chavez has a history in Nevada because of a previous failed test. In November 2009, he tested positive for Furosemide -- a diuretic typically used to help cut weight or used as a masking agent for steroids -- in conjunction with his fight against Troy Rowland, which took place on the Manny Pacquiao-Cotto undercard at the MGM Grand in Las Vegas.

For the positive test, which resulted from a pre-fight urine sample, the commission suspended Chavez for seven months and fined him $10,000 (10 percent of his $100,000 purse). The fight result, originally a lopsided decision win for Chavez, was changed to a no-decision.

Chavez's drug tests, or lack thereof, for recent fights in Texas also have come under heavy scrutiny, perhaps prompting Nevada officials to seek a random test for his first fight in Nevada since the 2009 bout against Rowland.

In the past few months, four notable boxers have tested positive for banned substances: junior welterweight titlist Lamont Peterson, former welterweight titlist Andre Berto, former light heavyweight champion Antonio Tarver and former cruiserweight titleholder Enzo Maccarinelli.