Michael Jackson took Propofol as early as 1999, a former manager has claimed in a new book.

In his new book, Frank Cascio, who became a friend to the King of Pop at age 5, wrote that he first saw Jackson take Propofol while on his Dangerous tour in 1993, The Associated Press reported.

Cascio also claimed that Jackson was under the influence of the drug ahead of his thirtieth anniversary concert in 2001, The AP added.

In the book titled My Friend Michael: An Ordinary Friendship with an Extraordinary Man, Cascio wrote that Jackson started the first of two anniversary shows an hour late because he was being drugged up in his dressing room.

My naive belief that Michael wouldn't let his medicine interfere with the show blew up in my face, Cascio writes, The AP reported. I can't begin to describe my disappointment and panic at this moment.

Jackson's personal doctor Conrad Murray, 58, was recently found guilty of involuntary manslaughter in the pop star's drug-related death. Jackson died in 2009 as a result of an overdose of Propofol, which is a surgical anesthetic.

Read the full AP report here.