Acting Inspector Darryl Lennane said in a statement that police and fire fighters wearing protective clothing attended the incident around lunchtime and police cordons were put in place.
Two plastic bags containing sand material were removed from the premises and the contents analysed.
A man who visited the building and left the packages indicated they contained radioactive material.
"Analysis showed that the material was monocote sand of the type found in Australian mines," Senior Sergeant Lennane said.
A package with the same contents was also delivered to the Green party's office in Stuart St, Dunedin, and also did not present any risk to public safety, he said.
A 45-year-old man was being spoken to by police in relation to the incident.
Earlier today, the second floor of Radio House on lower Stuart St was evacuated for about three hours.
Mrs Rich's secretary noticed a label of the package said 'medium radiation" and called police.
