POLICE have arrested a 40-year-old Adamstown man as part of an interstate cannabis trafficking operation.

Newcastle detectives and the NSW State Crime Command were called in to assist with a South Australian police investigation titled Operation Ditch after it was revealed the cannabis was allegedly being transported into Newcastle.

Subsequent police searches in Adamstown allegedly found about 8kg of cannabis and more than $65,000 cash in a Bailey Street storage unit and at a home on Brunker Road.

The Drug Investigation Branch-led operation was established to target the movement of drugs between South Australia, New South Wales and Queensland.

Raids across the three states in total netted about 30kg of cannabis, firearms, steroids, 88 cannabis plants and almost $500,000.

A 40-year-old Adamstown man was arrested on Wednesday morning and charged with deemed supply of prohibited drug.

He was granted bail in Newcastle Local Court and will re-appear on January 18 next year.

Six other people were arrested in South Australia and Queensland and charged with numerous offences.

Further charges are expected, police said.