KiwiRail says a freight train was halted south of Dunedin after the driver noticed smoke coming from underneath the locomotive this afternoon.
A KiwiRail spokesperson said as a safety precaution, the fire service was called to the scene, and water poured on to the locomotive to cool it down.
The train was cleared to resume its journey to Dunedin, where the locomotive would be inspected.
The spokesperson said at no point was there any fuel leak or any damage to the surrounding area.