Shore police on the ground in quake-hit Christchurch

North Shore police are among those who have been helping out in the earthquake-stricken city of Christchurch.

A Shore sergeant and 13 constables have been assisting for several days during an extended state of emergency.

Extra police and firefighters from Dunedin, Invercargill and Auckland remained in the area to help manage the situation including cracking down on looting in the severely damaged central business district.

The danger from falling debris has been one of the key concerns for police.

Much of the CBD remained cordoned off after the magnitude 7.1 earthquake early on Saturday.

The area remained unstable with aftershocks being felt for days afterwards including a 4.5 jolt at about 12.30pm on Monday.

An estimated 50,000 workers were affected by the cordons on Monday.

Christchurch mayor Bob Parker has warned it could be months before life returns to normal.

- © Fairfax NZ News