The Regional Illegal Dumping Squad has put out a call for assistance after 15 tonnes of asbestos-contaminated waste was discovered near Kurri Kurri.
Investigators suspect a tipper truck dumped the material on Hart Road, Loxford some time around Sunday, October 2.
Squad coordinator Rob Robertson said the culprit or culprits left clues at the site.
"One of the items that we found was an old birthday card to a young boy named Earl from Uncle Wayne, Aunty Liz, and Mandy," he stated.
"What we're hoping is, people might recognise the combination of those names and get in touch with us."
The quantity of waste found on the road has investigators looking at the possibility of a commercial dump, which carries penalties of up to $1 million for businesses found guilty.
Anyone with information is urged to contact the RID Squad on (02) 4921 0171.
