British actress Emma Watson has paid tribute to her 'lovely' Harry Potter co-star Dave Legeno, after he passed away aged 50 from heat stroke while hiking in Death Valley, California.

Legeno, who played werewolf Fenrir Greyback in three of the Harry Potter movies, was discovered by a pair of hikers in the remote wash below Manly Beacon, West of Zabriskie Point.

A helicopter was sent out recover the mixed martial arts expert's body, Inyo County officials confirmed.

County Deputy Coroner Jason Molinar said the actor's body may have been lying for days in triple-digit heat, as it was partially decomposed.

Taking to social media Watson, who rose to fame as Hermione Granger in the Harry Potter franchise, expressed her condolences. She starred alongside the former bouncer and wrestler in three Harry Potter films.

Meanwhile Harry Potter villainTom Felton, who played Draco Malfoy in all the films, described Legeno as a 'great talent' in a moving message on Instagram.

"Dave Legeno. It was always a pleasure. He was a great talent with a heart of gold and always had time for anyone," he said.

"Dave was a soft, kind gentleman off screen but had the skill to be the complete opposite on screen.

"He taught me lots, You will be missed mate xx #DaveLegeno."

Legeno, whose first major film role was in Guy Ritchie's Snatch, is survived by a 20-year-old daughter Wendy.