DULUTH — A semi driver suffered significant burns in an explosion inside his rig in Duluth.

Assistant Fire Chief Erik Simonson said waste oil was being transferred when a pump inside the semi backfired, igniting the collection of vapors Tuesday afternoon. The semi is from Rainy Lake Oil in International Falls.

Simonson said the driver suffered substantial second-degree burns to his upper torso. He was taken to a local hospital. His condition was not released.