Responding to published reports that Nathan Marquardt (Pictures) tested positive for steroids following his August 6 fight versus Ivan Salaverry (Pictures) in Las Vegas, UFC President Dana White told Sherdog.com Monday night that his company fully supports the young middleweight.

“He swears to God that he didn’t take steroids,” White said. “I believe him. I support him 100 percent. He said all he takes are supplements he buys in the health food store.”

“[Marquardt] was taking some supplements,” replied Marquardt’s long-time manager Will Hendricks when asked if the Denver, Colo.-based fighter used supplements that could be mistaken for banned performance enhancers. “I don’t really know what it was. That’s one thing they’re investigating right now.”

Marquardt was in Las Vegas Monday undergoing a new urinalysis; he also retested once in Colorado, according to White.

Hendricks told Sherdog.com his fighter “adamantly” denies the allegations put forward in the complaint from the Nevada State Athletic Commission and “believes there’s some problem with the test.”

MMAWeekly's Ivan Trembow broke the news Monday evening that Marquardt’s post-fight urinalysis showed a “significant” amount of nandrolone metabolite, commonly known as “Deca.”

When asked if to his knowledge Marquardt had ever used steroids, Hendricks answered, “Absolutely not. Never. He’d be the last person in the world that would take them.”

Marquardt, whose decision victory over Salaverry was the main event on the debut of SpikeTV’s “Ultimate Fight Night,” has 20 days after receiving the official complaint to respond. Should he do so, a hearing in front of the Nevada State Athletic Commission will be set at which time the five-member regulatory body would make a ruling.

If the results are upheld, Marquardt would join Josh Barnett (Pictures), Tim Sylvia (Pictures) and Kimo Leopoldo (Pictures) as UFC fighters that tested positive for steroids in Nevada.