Update 8.15pm: helicopters are back in the air after the drone was located and is no longer flying.
All six helicopters fighting a fire in the Lee Valley have been grounded because of a drone sighted in the area.
A seventh helicopter has also been stood down before it reached the fireground.
The fire is burning over about five hectares of a pine forestry block and is not yet contained. Firefighters are unable to continue the firefight using ground attack while the helicopters are grounded because the terrain is too steep and dangerous.
Police are actively seeking the drone operator.
Fire and Emergency Incident Controller Steve Trigg says drones are a safety risk to aerial firefighting, as a mid-air collision with a drone could have fatal consequences.
"The drone sighting has completely impacted helicopter operations. Firefighting efforts are on hold until the safety of air operations can be assured," Steve says.
Police have evacuated 11 houses in response to the "significant vegetation fire" in Lee Valley that has not yet been contained.
FENZ says the evacuated homes were on River Terrace between the Lee Valley Bridge over the Wairoa River and Mead Road.
"Nelson Tasman Civil Defence has opened a civil defence centre for evacuees at the Wanderers’ Clubrooms on Lord Rutherford Drive," FENZ says.
"Further information on that support is available by calling 03 543 8400."
FENZ says nine brigades were responding to the fire, which they were called to just before 3:30pm on Wednesday.
It says crews were also being supported by helicopters with monsoon buckets.
"As at 5.30pm the fire is estimated to have covered about three hectares and is not yet contained," FENZ says.
"We ask people to stay well away from the area so emergency services are not held up by non-essential traffic.
"Also those with drones must not fly them in the area – when drones are spotted the helicopters have to be grounded for safety reasons."
Earlier, a FENZ spokesperson said there were three separate areas of fire, spreading uphill into a pine plantation.
Five helicopters were supporting ground crews from Brightwater, Appleby, Richmond, Wakefield, Upper Moutere and Nelson.
People in the area were urgently asked to avoid non-essential travel, particularly on Paton Rd, as traffic congestion was delaying fire trucks from reaching the scene.
A Police spokesperson says they were alerted to the fire at 3:50pm.
"Police were involved to evacuate nearby properties and it appears there is a cordon at the intersection of Lee Valley Rd and Wairoa Valley Rd."
