Residents have told how they were evacuated from their homes after the bomb squad were called to a city flat.
A section of King Street between University Road and Linksfield Road was sealed off late on Saturday night.
The road was closed by police between 11pm and 5am yesterday.
Nearby flats, the Bobbin pub and the Tesco Express garage were evacuated by officers for around two hours.
A 26-year-old man was arrested and a “number of unidentified items” had been removed from a property between the pub and the petrol station.
Police were still at the scene yesterday, with an officer standing guard at the building at the centre of the incident.
Helen Cauls and her flatmates were evacuated and waited on King Street for two hours before getting the all-clear to return home.
Helen, 22, said: “We were told to leave and we just waited in the street at around 11pm.
“We came back at 1am and asked the police if they could tell us what happened, but they wouldn’t say.
“Apparently they brought in two different bomb disposal vans and dogs.”
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One man, who did not want to be named, said: “There was a lot of bomb disposal guys here, maybe 12 of them.”
A Police Scotland spokesman said a probe to establish the “exact nature” of the materials found had begun.
He said: “The items were recovered from the property after they were discovered during Saturday evening.
“Inquiries are ongoing to establish the exact nature of these items and officers are currently liaising with specialist partner agencies.”
Chief Inspector Darren Bruce of North East Police Division said: “This incident was contained to one property and there was no immediate risk to the wider public.
“A police presence is likely to remain in the area over the coming days.”
The Ministry of Defence was unable to comment on the incident.