One firefighter was also understood to have suffered from smoke inhalation.
"One patient was taken to Christchurch Hospital in a moderate condition," St John said.
Fire and Emergency said it was also asking people to be extra vigilant about fire risk over the next few days with scorching temperatures up to 36C forecast tomorrow.
"Put off lighting any fires in the open if you are in a prohibited fire season and ensure braziers, pizza ovens and charcoal fires are supervised and completely extinguished," he said.
"We are asking builders and contractors to take extra care using power tools that might cause sparks in the open air."
"This is particularly important for grinding and cutting metals, especially if they are near vegetation."
It came as quick-thinking firefighters earlier saved a dozen at-risk properties in a separate fire further south in Christchurch's coastal Redcliffs suburb as temperatures hit 28C.
Redcliffs residents had earlier been on edge as the uncontrolled fire crept closer to suburban homes.
Six fire crews and two helicopters were now tackling the large scrub fire on Balmoral Hill, near Glentrae Rd, which broke out around 1.40pm.
Fire and Emergency's Darren Aitken said quick thinking by those on the ground saved dozens of at-risk properties.
He said firefighters could be seen on the scaffolding of a construction site, and other firefighters were on the decks of other properties trying to protect them.
At 2pm temperatures were sitting near 27C in the Garden City.
A helicopter was in attendance at the fire. Photo / George Heard
Christchurch City councillor Aaron Keown said he could see heavy smoke coming up over Mt Pleasant and into Heathcote.
It comes after a scrub fire chewed through 15ha in the hills above Cass Bay last Tuesday.
Twenty homes were evacuated as a trio of helicopters with monsoon buckets tried to contain the blaze.
Fire services are still investigating what sparked the fire.
