Four people, including two adults, a teen and an infant, have been found frozen to death about 40 feet from the U.S.-Canada border while being smuggled into North Dakota, according to U.S. and Canadian authorities.

U.S. Customs and Border Protection officers and law enforcement officers with the Department of Homeland Security performed a traffic stop Jan. 19 on a 15-passenger van about 1 mile from the border when they found two undocumented Indian nationals from Canada inside, according to the Manitoba Royal Canadian Mounted Police.

Less than a quarter mile away from the border, law enforcement encountered and apprehended five additional undocumented Indian nationals that walked across the U.S. border from Manitoba, Canada, according to the RCMP.

One of the travelers who was taken into custody was carrying a backpack containing children’s items, such as clothes, diapers and toys, according to the U.S. Department of Justice. He told authorities he was carrying the backpack for a family that was traveling with their group but got separated from them as they traveled to the border during the night.

The Royal Canadian Mounted Police, coordinating with the U.S. Customs and Border Protection, began a search on both sides of the border for additional travelers when they found the bodies of four individuals on the Canadian side of the border in Manitoba.

The adult male, adult female, teen male and infant were found “frozen,” according to Canadian authorities, and are believed to have died due to exposure.

The DOJ said, according to the group of travelers, the border crossing took an estimated 11 hours. Two of the travelers were transported to a hospital with serious injuries, the DOJ said.

The low temperature in Emerson, Manitoba, which is at the U.S.-Canada border, dipped to minus 13 degrees Fahrenheit on Wednesday.

Steve Shand, 47, a U.S. citizen from Florida who was driving the van, was arrested by U.S. Border Patrol and charged with one count of knowing or in reckless disregard of the fact that an alien had come to, entered, or remained in the United States in violation of law, having transported and moved or having attempted to transport and move such aliens, according to the U.S. Department of Justice.

Shand made his first court appearance Thursday and is due back in court on Jan. 24. He is currently being held in custody in Grand Forks County in North Dakota.

An autopsy will be conducted to determine cause of death of the victims. The four travelers who died have not yet been identified.

The Mounted Police said it plans to continue searching for any additional people who may have been illegally crossing the border.