Heath Ledger's initial autopsy might not have thrown up any clues as to why he died, but NYPD sources might have put their finger on one possible answer.

According to TMZ, five different types of pills were found in the apartment where Heath Ledger died - all prescibed to him - including Valium, Lorazepam, Xanax and two different types of sleeping pills.

However, while we await the toxicology report that's due late last week, pneumonia has been resolutely ruled out as a cause of Heath Ledger's sudden death.

While the world is still trying to get its head around yesterday's sudden death of Heath Ledger, it's already time to start figuring out exactly what killed him.

The autopsy on Heath Ledger's body will take place today, meaning that it shouldn't be long before we know which of the conflicting stories about Heath Ledger's death - was it suicide? An accidental overdose? Pneumonia? - is most accurate.

Meanwhile, tributes have been pouring in from Heath's admirers, friends and family.