A body found Monday in a remote desert campsite is that of former Ultimate Fighting champion Evan Tanner, his manager told FOXNews.com.

Tanner, 37, disappeared last week while camping in a rugged area of Imperial County near the California-Arizona border.

"I really think what happened here is that he got in over his head out in the 115-degree desert and had a problem with exposure," Tanner's manager John Hayner of Driving Force Sports said Tuesday.

A preliminary coroner's report suggests Tanner died of heat exposure, Imperial County sheriff's Lt. George Moreno said.

A helicopter pilot spotted the body Monday about two miles from his campsite, officials said.

Click here for Evan Tanner's fighter page at UFC.com.

Click here for Tanner's biography at UFC.com.

Click here for photos.

Tanner was a UFC middleweight champion and a United States Wrestling Federation heavyweight champion. The UFC and Driving Force Sports had memorials to the fighter on their Web sites Tuesday.

"As an extreme ultimate fighter, practicing mixed martial arts, he really didn’t define himself as being a fighter," Hayner told FOXNews.com. "He defined himself as being an adventurer, and he would fund his adventures through fighting."

A native of Amarillo, Texas, Tanner scored 34 wins and lost eight times during his UFC career. He clinched the UFC middleweight championship in 2005 by defeating David Terrell.

In recent months, his mind had been on risky expeditions, according to Hayner.

"This summer he wanted to go kayaking from Alaska to California, and I said, 'Evan, that’s incredibly dangerous; you could die out there," the manager told FOXNews.com. "And he goes, 'Well, you could die anywhere.'

"He always had this kind of concept [of], well, it sharpens your senses by being on a razor's edge with your life actually on the line."

In an Aug. 16 posting on his blog at Spike.com titled "Treasure hunting in the desert," Tanner wrote about his desire to explore the Southern California terrain.

"The idea of going into the desert came to me soon after I moved to Oceanside," he wrote. "It was motivated by my friend Sara's talk of treasure hunting and lost gold, and my own insatiable appetite for adventure and exploration."

Tanner described his fascination with the desert and his preparations for the trip.

"I plan on going so deep into the desert that any failure of my equipment could cost me my life," he wrote.

Click here to read the blog.

The Imperial Valley Press Online reported that the campsite was discovered in the Clapp Springs area of the Palo Verde Mountains, about 60 miles northeast of Brawley, Calif.

Sheriff's officials said family members had been keeping in touch with Tanner through text messages since he left on Wednesday, and became concerned when he stopped responding.

Hayner said Tanner called a friend's wife on Sept. 3 to say his dirt bike had run out of gas and he was going to walk to get some.

Crews had been searching for Tanner since Friday.

Temperatures in the area were very high during the weekend, topping out at 114 on Sunday, Moreno said.

Click here to read more at the Imperial Valley Press Online.

FOXNews.com's Sara Bonisteel and the Associated Press contributed to this report.