ST. PAUL, Minn. (AP) -

The shipping season has opened much later than normal on the Upper Mississippi River, due to thick ice on Lake Pepin.

The U.S. Army Corps of Engineers says the first tow of the season broke through more than 12 to 16 inches of ice on Lake Pepin early Monday. The Roberta Tabor, pushing 12 barges, went through Lock and Dam 2 in Hastings shortly after 8 p.m. on its way to St. Paul.

The Roberta Tabor is owned by American River Transportation Co. in St. Louis.

The Corps says the average opening date of the navigation season for the last 30 years has been March 20. Last year, the first tow of the season arrived March 17.

Before now, the latest arrival date unrelated to flooding was April 4, 2008.