Police are continuing their investigation into the death of four people at a Bicknell Court property in Broadmeadows on June 26.
In a statement, police said that forensic testing remains ongoing however preliminary tests confirmed that a synthetic opioid was in all four peoples systems.
No presence of fentanyl has been detected as of yet.
The deaths of the 37-year-old man, 32-year-old man, 17-year-old boy and 42-year-old woman are not being treated as suspicious
Anyone with information about the supply of illicit drugs is asked to contact crime Stoppers on 1800 333 000 or submit a confidential report at www.crimestoppers.com.au
