Cause of Port Hills fires 'undetermined' but both believed to be 'deliberately lit'

The final cause of Port Hills fires in Christchurch almost a year ago is "undetermined", says Fire and Emergency New Zealand.

"The lack of physical evidence or being able to interview anyone responsible has made it very difficult to determine the cause and origin conclusively," Fire and Emergency said today.

"However, Fire and Emergency New Zealand believes both were deliberately lit and the matter remains in the hands of the police," it said.

Fire and Emergency New Zealand's investigation into the fires has been completed and closed.

It will only reopen if there's new evidence.

Two Port Hills fires broke out on February 13 and merged before burning through 1600 hectares of land and claiming nine homes and damaging five others. A helicopter pilot died in a crash while fighting the fire.

It took 66 days before the fire was declared fully extinguished.