A truck caught fire on Auckland's motorway near Bombay earlier today, producing plumes of dense smoke that could be seen from Papakura, bringing vehicles to a standstill and causing long delays.

At 2.45pm, Waka Kotahi said the fire was under control but the road would remain closed for "some time" as debris was cleared.

There were 45-minute northbound delays between Pokeno and Bombay as of 2pm.

Footage showed flames engulfing the front cabin of a two-trailer truck in the middle of the northbound highway lanes.

Patrol cars blocked off the road several metres behind the truck, stopping traffic, while some motorists parked their cars and stood on the side of the road.

A truck has caught fire on State Highway 1 south of Auckland. Photo / Supplied

A police spokesperson said there had been no reports of injuries following the incident, which happened just before the Ramarama off-ramp. Waka Kotahi first reported the incident at 1.15pm.

Journalist Will Trafford, who was at the scene at the time, said really dense black smoke could be seen from as far away as Papakura, and the motorway was "completely blocked".

At least five police cars and three fire trucks were at the site.

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Vehicles were stationary with traffic backed up 4km towards Pukekohe. Many people were getting out of the cars to take a look at what was happening, he said. Vehicles that were queued up on Mill Rd were doing U-turns and heading back toward Pukekohe.

Motorists have been asked to consider exiting to Nikau Rd to rejoin the highway at the Ramarama Interchange via Razorback Rd, Bombay Rd and Great South Rd.

Those travelling south are told to expect up to 15-minute delays southbound through the area.

A police spokesperson said at this stage there were no reports of injuries and St John confirmed paramedics had not been called to respond to the incident.

Northbound lanes have been closed between the Bombay and Ramarama off-ramp.