Authorities in Canada and the United States say they have thwarted a human smuggling attempt near Sarnia.

U.S. Customs and Border Protection says its agents saw two men board a boat in Port Huron on Aug. 26 and head across the St. Clair River towards Sarnia.

CBP spokesman Kris Grogan says the agents contacted the RCMP, who reported seeing at least four people board the same boat on the Canadian side of the river.

The boat then made its way back to Port Huron, where six individuals -- all Polish citizens -- were stopped by U.S. border agents.

Grogan says that when questioned, they admitted to being in the United States illegally.

He says Piotr Lisiecki, who was allegedly piloting the boat, faces one count of improper entry into the U.S. by an alien and one count of bringing in and harbouring aliens.

Mona Dolinska, Maria Hauf, Jan Hauf, Roman Kowalski, and Wanda Kowalska each face a charge of improper entry into the U.S. by an alien.

The six accused will be prosecuted by the U.S. attorney's office in Michigan.