Parramatta Police Area Command discovered the body inside, establishing a crime scene.
She is yet to be identified, detectives are treating the death as suspicious.
A strike force has been setup to investigated the death, with homicide squads taking charge.
NSW Police released a statement of a man's description who remains the top suspect.
"The man is described as being aged about 20, 175cm-180cm tall, 80kg-90kg with a muscular/athletic build. The man has black hair, a short beard and moustache," the statement read.
"When last seen he was wearing a black, sleeveless top and jeans. He may have scratches on his face and arms."
Officers also say the man could be occupying a Mitsubishi Fuso tipper truck, NSW registration MAKKAC.
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