Michael Jackson used potent drugs to sleep

BEIJING, July 3 (Xinhuanet) -- As it is yet to establish what caused the death of Michael Jackson last Thursday, sources close to the pop star revealed that he was routinely using potent drugs to combat insomnia in the past.

Pop star Michael Jackson rehearses for his planned shows in London at the Staples Center in Los Angeles, California in this handout photo taken June 23, 2009. (Xinhua/Reuters, File Photo)

The accounts of the sources raise the possibility that drugs may have contributed to singer's death.

Sources told CNN Thursday, Michael Jackson traveled with what amounted to a "mini-clinic," complete with an IV pole and an anesthesiologist who medicated the insomniac singer, during his HIStory tour in the mid-90s.

They said that Michael was -- at least in the past -- routinely administered potent drugs to help him sleep.