Fire crews are working to find out what caused smoke in the cockpit of a passenger plane.

An Air New Zealand plane has had to make an emergency landing at Christchurch Airport.

A Fire and Emergency spokesman says it landed safely and all passengers have disembarked.

He says it's not obvious at this stage what caused the smoke.

An Air New Zealand spokesperson said Flight NZ5751 from Christchurch to Dunedin returned to Christchurch after a smoke indicator warning light illuminated.

The aircraft landed safely shortly before 2.40pm and customers were immediately disembarked onto the tarmac as a precaution.

The aircraft is now being checked following the incident.

Last week an Air New Zealand Q300 aircraft from Wellington to Christchurch shut down an engine after smoke was seen coming from it.

Passengers were reported to be praying on the flight after hearing a loud bang seeing smoke.

More to come