The Royal Canadian Mounted Police said the accident happened around 10:30 p.m. Tuesday outside the town of Gillam, some 650 miles north of Winnipeg, CTV News reported.
The unidentified 46-year-old tanker driver told police when he swerved to avoid an oncoming vehicle at the crest of a hill, some of the trailer's wheels dropped off the edge of the road and it overturned.
The driver received only minor injuries and a passing driver gave him a ride into Gillam, where he called police, the Canadian Broadcasting Corp. said.
The driver of the vehicle that caused the trucker to swerve didn't stop, the RCMP said.
The highway was closed all night and into Wednesday for environmental cleanup, the reports said.