Reed Saxon, Associated Press
Heath Ledger

Six different types of prescription drugs were found in Heath Ledger's New York apartment — including anti-anxiety medications and sleeping pills — though the cause of his death won't be known for several days after a preliminary autopsy Wednesday was inconclusive, authorities said.

A rolled-up $20 bill was also found on the floor near the Australian actor's bed, but lab tests detected no traces of drug residue. Police also said no illegal drugs were found in the apartment.

Among the prescription medications found were pills to treat insomnia and anxiety, and an antihistamine, according to two law enforcement officials who spoke on condition of anonymity because the investigation is ongoing. Three of the drugs were prescribed in Europe, the sources said.

The $20 bill was found on the floor near Ledger's bed, NYPD spokesman Paul Browne said lab tests found nothing to indicate it had been used to snort drugs.

The Australian-born actor, 28, was found dead Tuesday by his housekeeper and a massage therapist. The pills were found in bottles in Ledger's bedroom and bathroom, and police said the death was caused by a possible drug overdose and appeared to be accidental.