Officers said they seized materials that can be used to make petrol bombs including thinner, naphtha, magnesium and aluminium powder, as well as glass bottles.
Two students were among the five people – aged between 17 and 31 – who were arrested.
Police said they went to the building at around 10pm following a tip-off, arresting two men in the lobby.
Officers then smashed their way inside a unit when nobody opened the door.
Three men were inside at the time, police said, and two climbed out of a window. The pair had to be coaxed back inside via mediation from firefighters sent to the scene.
Police said they believe the items seized are connected to the city’s ongoing protest movement.