WHILE investigating the murder last month of South Grafton woman Michelle Roberts, police made a possible breakthrough in the unsolved pizza boy robberies.
Two knives were found in bush in the Margaret St area where police and SES searched for clues into the murder, of which South Grafton man Andrew Sumpton was later charged.
However, the knives have been linked by police to a different case.
Investigators have been hunting for robbers who targeted pizza deliverers in Grafton in December 2011 and January this year and last month released an image of a male they wished to speak to.
Responding to Daily Examiner inquiries, Detective Sergeant Grahame Burke confirmed police believed "one or both" knives could be related to the pizza boy robberies.
"The knives will undergo forensic examination," Det Sgt Burke said, adding inquiries were continuing.
The first robbery was in Bacon St, Grafton on December 10, the second involved a Dominos Pizza driver on January 29 in Bent St, South Grafton and the third was in Bent St, involving an Eagle Boys driver on January 31.
Anyone with information is urged to contact Grafton Police or Crime Stoppers on 1800 333 000.