Fire crews have left the scene of a fire, in the 21st floor of the newly opened Commercial Bay shopping centre in Auckland's CBD

Fire and Emergency says a fire in a two by one metre skip on the multi-million dollar high rise construction site, set off the building's sprinklers and alerted emergency services just after 11 last night.

Smoke had spread through the lobby of the building, triggering a third alarm.

The fire was contained to the 21st floor by the building's sprinkler system.

Fourteen crews attended, and the last crew left the scene about 1.30am.

A Fletcher construction site manager says they had no workers in the tower at the time of the blaze.