A car on fire near Auckland's Southern Motorway has caused delays for motorists this morning.

Photo: NZTA

Police said no-one was in the car when the fire was reported.

They said it is unclear how the fire started.

SH20 SOUTHWESTERN MWY, EASTBOUND - 6.40AM

Extra caution is advised near the SH20 link to SH1 due to a car fire blocking the left eastbound lane. Please pass the incident with care and expect some delays. ^MF pic.twitter.com/dP1SqAGGmx — NZTA Akld & Nthlnd (@NZTAAkl) April 22, 2019

The car is reported to be just off the motorway, where State Highway 1 connects with State Highway 20, near Lambie Drive.

Motorists have been advised to expect delays.

Meanwhile, three cars caught fire at a petrol station in Invercargill this morning.

No one was injured and the blaze, which did not pose a risk to the stored fuel, was brought under control.

Fire and Emergency's Brent Dunn said three fire engines responded to the fire at Northern Auto Services about 4.30am.

He said a fire investigator would arrive at first light.