A pile of rubble where Christchurch's former police station once stood will stay there for the next five weeks.

That's how long it will take to clean up the mess, following the demolition of the building over the weekend.

Demolition company Ceres NZ spokesman Bernie de Vere says the massive pile of dust is perfectly safe - and poses no risk to members of the public.

"That is just straight concrete dust.

"There's no asbestos or anything like that in the building. It's been absolutely worked on for 10 months."