The biggest border crossing south of Winnipeg into the United States is refusing to admit travellers because a snow storm has closed the highway on the North Dakota side.

'There's no place for people to drive, so we've been sending them back up the highway to Canada.' —U.S. border agent

Interstate 29 was shut down Friday from the Canadian border south through South Dakota all the way to Iowa. It isn't expected to reopen until at least Saturday, so U.S. border agents will continue to turn back anyone trying to enter the country at the crossing between Emerson, Man., and Pembina, N.D.

A U.S. Customs and Border Protection officer at the Pembina post said agents have had to turn back a constant stream of frustrated travellers. It's not his agency's decision, he stressed, because highway jurisdiction lies with the North Dakota Department of Transportation.

"It's been non-stop, but there's nothing we can do about it. It's an arrestable offence to drive on an interstate that's closed," said the agent, who wouldn't give his name because he's not authorized to talk to the media.

"There's no place for people to drive, so we've been sending them back up the highway to Canada. The highway's closed, that's the only reason."

Interstate 29 runs south from its border junction with Highway 75, which stretches from the southern outskirts of Winnipeg down to the U.S. frontier.

The Canadian border post at Emerson is still open for whatever travellers and vehicles manage to get there, an officer with the Canada Border Services Agency said.

Environment Canada says the storm is expected to drop 10 centimetres of snow on the Emerson area Friday night, and a similar amount in regions further north by Saturday morning.