WELLINGTON (Reuters) - Hundreds of firefighters and dozens of aircraft fought a massive wildfire threatening New Zealand’s third largest city Christchurch on Thursday.

The wildfire in Christchurch’s Port Hills district spread rapidly overnight to cover more than 1,800 hectares (4,447 acres), emergency workers said.

More than 1,000 people were evacuated from their homes, 11 properties were destroyed and a state of emergency was declared.

“There’s a whole lot of people here who have been traumatized by the events, some who have lost their homes, many have been evacuated,” Prime Minister Bill English told reporters in Christchurch after cancelling all his engagements to fly to the South Island city.

He said it could take up to a week before the fire was fully under control, but that the blaze had been contained on Thursday and was not spreading further.

Seventeen helicopters and fixed wing aircraft were dispatched amid forecasts for winds that could fan the flames.

The crew from a U.S. coast guard ship which had been docked in the nearby port of Lyttleton were helping local defense forces.

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“The situation remains very serious,” said David Adamson, Christchurch Civil Defence Controller. “Police and the Defence Force have had a huge job overnight with evacuations, the setting-up of cordons around key areas and security patrols of areas that have been evacuated.”

A change in the wind direction is predicted for later in the week that will lower temperatures and humidity and could slow the fire’s progress, emergency workers said.

A helicopter pilot died on Tuesday after crashing while tackling the blaze.

The cause of the fire was not yet known and authorities were investigating. The prime minister said two fires had started at the same time which he described as “suspicious” but that he did not want people to “jump to conclusions”