Staff at an Auckland building site have been sent home for the day and Worksafe is investigating after a construction worker fell five storeys down a lift shaft.

The incident happened at a supermarket construction site on the corner of Pollen Street and Williamson Avenue in Ponsonby.

It took fire-fighters and ambulance staff around half an hour to extract the man.

He's now in a critical condition in hospital.

Fire Service spokesman Scott Osmond said the construction worker has fallen more than 15 metres.