A state of emergency in Christchurch's Port Hills has been extended as fires in the area keep firefighters busy, despite being contained.

Residents of two roads in Christchurch's Port Hills kept out of their home by the massive blaze over the last week were allowed back on Tuesday morning.

Cordons closing dozens of homes on Kennedys Bush and Hoon Hay Valley Roads were lifted from 8am, with access strictly restricted to residents.

But Christchurch Mayor Lianne Dalziel said with many other residents still unable to return and a risk of potential for flare-ups still looming, Christchurch City and Selwyn District had opted to continue the state of emergency on Tuesday afternoon.

"There is always the risk that further evacuations could be required," she said.

"The fire is still being fought on the ground and in the air. The environment remains volatile inside the controlled area. The fire is not out and there are extensive hotspots to deal with."

She said agencies were also still responding to those dealing with the trauma of losing homes and other damage.

The state of emergency lasts a week, but can be cut short.

On Monday evening, 154 properties were behind the cordon on Kennedys Bush Rd, Hoon Hay Valley Rd, Summit Road and parts of Worsley Rd.

Up to 150 firefighters are still on site to quell the 2075ha blaze which started on Monday night last week.

Officials say burned forestry areas are now at risk of rockfall. Large boulders above Dyers Pass Rd are being moved into holes excavated beneath.