One of the greatest singers of all time was found dead in the bathtub of the Beverly Hills Hilton this weekend. Award-winning singer Whitney Houston died of unknown causes Saturday afternoon. The "I Will Always Love You" crooner, who appeared in such hit films as The Bodyguard, Waiting to Exhale and The Preacher's Wife, was unresponsive when a member of her entourage discovered her in the bathroom of the upscale hotel. An autopsy will determine whether it was drugs, drowning or something else that caused her death. Although numerous prescription pills were found in the 48-year-old's hotel room, TMZ is reporting that no illegal drugs or alcohol were uncovered. Insiders tell TMZ that Houston had been "partying heavily" the night before at the hotel. She was supposedly drinking and chatting with pals the prior evening. Houston was scheduled to perform at Clive Davis' pre-Grammy party. Both Houston's 18-year-old daughter Bobbi Kristina and cousin Dionne Warwick were denied entrance to her hotel room and not permitted to see Houston's body. Houston's only daughter was devastated when she was turned away, screaming, cursing and demanding to see her late mom. Houston's untimely death has rocked the music industry, Hollywood and the world. The Recording Academy released the following statement, "Six-time GRAMMY(r) winner Whitney Houston was one of the world's greatest pop singers of all time who leaves behind a robust musical soundtrack spanning the past three decades. Her powerful voice graced many memorable and award-winning songs. A light has been dimmed in our music community today, and we extend our deepest condolences to her family, friends, fans and all who have been touched by her beautiful voice." Over the past decade, Houston struggled with substance abuse. Her last stint in rehab was this past May when she was treated for crack addiction.