HONG KONG -- Taiwanese director Ang Lee mourned the death of Heath Ledger, saying working with the Australian-born actor was "one of the purest joys of my life."

Ledger costarred with Jake Gyllenhaal in Lee's Oscar-winning movie "Brokeback Mountain." He played Ennis Del Mar in the gay romance about two ranch hands who carried on a secret love affair.

"Working with Heath was one of the purest joys of my life. He brought to the role of Ennis more than any of us could have imagined -- a thirst for life, for love, and for truth, and a vulnerability that made everyone who knew him love him. His death is heartbreaking," Lee said in an email to The Associated Press.

Ledger's performance in "Brokeback Mountain" earned him a best actor Oscar nomination. Lee garnered the best director award for the film.

The 28-year-old actor was found dead Tuesday by his housekeeper and masseuse in New York City -- lying naked and face-down at the foot of his bed, with prescription sleeping pills nearby, police said.

An initial autopsy on the actor was inconclusive.