Asbestos was found dumped in Old Northern Road, Dural on Monday.
Police said the material, found on an acreage property, was placed there between 3am and 2.18pm.
The property’s owner said he feared it could be asbestos when he noticed fibro-like substances among the rubble.
Fire & Rescue officers were called and contained the material.
Police and the council later had it removed safely.
Police said asbestos was a dangerous substance and urged anyone who suspected it was on their property or in their street, to stay away from it and contact the police or their council immediately.
They also said dumping asbestos was a serious offence and urged anyone with any information about the incident to contact Hills detectives on 9680 5399 or Crime Stoppers on 1800 333 000.