US police have confirmed that hikers found the body of the 50-year-old, best known for playing werewolf Fenrir Greyback in the Potter films, in the early hours of last Sunday.
The body had to be recovered from the remote area by helicopter.
The cause of death is believed to be heat-related, according to the local sheriff's department.
"The Inyo County Coroner will determine the final cause of death," a spokesman added.
"There are no signs of foul play."
Legeno, who was also a mixed martial artist, previously appeared in Guy Ritchie's film Snatch and in Batman Begins. He was set to star in upcoming film Sword of Vengeance.
His Harry Potter co-star Tom Felton, who played Draco Malfoy, paid tribute on Twitter.
He said: "Gutted to hear the sad news about Dave Legeno. He was a true Big, Friendly, Gentleman. Was a pleasure every time we met #BFG #DaveLegeno."