A freight train hauling volatile materials and other cargo derailed early Wednesday in northern Minnesota, authorities said.

The 15-car derailment of the southbound 107-car train, operated by Canadian National Railway, occurred about 3:20 a.m. roughly 25 miles northwest of Duluth, the St. Louis County Sheriff’s Office and a rail spokesman said.

“No breach or loss of hazardous materials occurred,” the Sheriff’s Office said in a statement. No injuries were reported.

“Three of the involved cars are carrying hazardous materials, but the cars are intact and there are no leaks,” said rail spokesman Patrick Waldron. The remaining derailed cars were either empty or carrying plastic pellets.

Waldron identified the hazardous materials, heading from Winnipeg to Superior, Wis., as:

Naphthalene, used as an insect repellent and best known as the active ingredient in mothballs.

Biphenyl, used in heat transfer fluids, food preservatives, and was an intermediate for polychlorinated biphenyls (PCBs) until banned.

Octene, used in production of polyethylene, the world’s most widely used plastic.

While the Sheriff’s Office statement read that “there is no danger to public safety,” County Emergency Services Manager Scott Camps said later that there is a “potential for release [of hazardous materials] when they have to offload the product from the damaged cars.”

Rail crews were cleaning up the scene “in bitter winter conditions” near Saginaw throughout the morning, Waldron said.

There was no word so far on what led to the derailment.