Discovery

Law enforcement sources tell TMZ the $20 that cops found in Heath Ledger’s apartment was clean — it did not contain drug residue.

Cops recovered the bill, tested it, and the results were clean.

TMZ has learned what types of pills were discovered in the apartment where Heath Ledger was found dead.

NYPD sources tell TMZ that nearly full pill bottles containing the anti-anxiety medications Alprazolam (Xanax), Diazepam (Valium) and Lorazepam (Ativan) were found in the apartment. The sleeping medication Zoplicone (Lunesta) and the sedative Temazepam (Restoril) — which is used by people with “debilitating insomnia” — were also found.

All of the drugs were prescribed to Ledger.

Meanwhile, Michelle Williams has just returned to Brooklyn with her two-year-old daughter, Matilda.

Her mother, sister and friends are gathered at the house where she once lived with Heath Ledger.

She and Matilda just arrived on a flight from Gothenburg, Sweden.