A southbound train has sparked a series of scrub fires outside of Christchurch.

The Dunedin-bound train was stopped just north of Rolleston after it caused the outbreak of about five fires in trackside vegetation by State Highway One near Templeton.

Five fire engines and two tankers rushed to the scene about 12.40pm.

The biggest fire spread over about 50m x 50m, Fire and Emergency New Zealand spokesman Andrew Norris said.

The fires are now under control.

The train was stopped north of Rolleston where it was checked and the cause of the sparks identified.

Norris said the train has been cleared and has now continued on its way south.

He said the cause could've come from a range of issues, including wagon brakes jammed on or hot exhaust fumes.

KiwiRail has been approached for comment.

Main South Rd was closed for a short period but is now open to traffic in both directions, Christchurch Transport Operations Centre (CTOC) said.