UFC light heavyweight champion Jon Jones passed multiple fight night drug tests on Dec. 29, after defeating Alexander Gustafsson at UFC 232 in Los Angeles.

California State Athletic Commission executive director Andy Foster told ESPN on Thursday that Jones, 31, was tested by both the United States Anti-Doping Agency (USADA) and the commission, and all tests have come back negative of banned substances.

Notably, both tests were negative for the M3 metabolite, which was the source of much prefight controversy and speculation.

"I can only go by what the scientists have told me," Foster told ESPN. "And what this tells me is that on the night of the fight, and leading up to the fight, Jon Jones was not doping."

UFC 232 was originally scheduled to take place in Las Vegas. On Dec. 9, however, Jones submitted a drug test to USADA that tested positive for a very trace amount of M3 metabolite, which is a byproduct of a chlorinated steroid.

After consulting multiple experts, USADA ruled the positive test was most likely caused by a residual amount of the M3 metabolite, left over from a positive test Jones submitted in July 2017 and was already sanctioned for. Despite USADA's ruling, the Nevada State Athletic Commission did not feel it had enough time to hold a hearing on the matter, and the UFC elected to move the entire event from Nevada to California, where the commission was more familiar with Jones' case.

Foster agreed to move forward with the event after experts said there was no evidence Jones had re-ingested any steroid and that the trace amount of the metabolite, found at a picogram per milliliter level, offered no performance-enhancing benefits.

On the night of the fight, however, Foster ordered his own drug tests of Jones, in addition to the USADA program administered by the UFC.

The commission's test was analyzed by the UCLA Olympic Analytical Laboratory, while USADA's was analyzed at the Sports Medicine Research and Testing Laboratory in Salt Lake City. Foster went so far as to collect both samples from the same urine stream from Jones on fight night, to eliminate as many variables as possible.

Jones has served two drug-related suspensions in his career, but has adamantly denied ever knowingly taken a banned substance. He argued a 2016 failed test was the result of a tainted sexual enhancement pill. He has not been able to identify the source of the 2017 failed test.

Leading up to UFC 232, Jones said he's been informed the trace amount of M3 metabolite could stay in his system for up to seven years, and the results of his Dec. 9 test shouldn't have even been made public because USADA does not consider them a failed test.

"They probably shouldn't have even been brought up," Jones said. "It's such a small amount that it has no effect. I think the professionals, whether it's USADA or the UFC, are realizing, 'Jon is kind of like a guinea pig in this situation.' I was almost wronged in this situation."

Jones is scheduled to appear before the Nevada commission on Jan. 29 to apply for a license in that state. The UFC has already announced he will face Anthony Smith in the main event of UFC 235 on March 2 at T-Mobile Arena in Las Vegas, provided he's granted a license.

Jeff Novitzky, the UFC vice president of athlete health and performance, told ESPN that the fight night results "validate" the UFC and CSAC's decision to move forward with the championship fight.

Novitzky also said that going into 2019, Jones could be the most frequently tested athlete in the world, as he is subject to the UFC's year-round program, athletic commission testing, and the Voluntary Anti-Doping Association (VADA) program, which he enrolled in last month.

"Jon has been, and will continue to be, likely the most tested professional athlete on the planet," Novitzky said. "And the UFC and VADA's testing will be transparent, so any fans or critics can see what Jones' results will be, as the most-tested athlete. I would encourage them to follow those results. Nothing is going to be hidden from anybody."