FOND DU LAC COUNTY, Wis. (WTAQ) - A Milwaukee 7th-grader died Monday after he spent 45 minutes underwater in Mauthe Lake in Fond du Lac County.

Authorities said the 12-year-old boy and two classmates were in the deep end of the lake’s designated swimming area when he lost his grip on one of the boys, and went under. A rescue diver from the Kewaskum Fire Department found the body in 10 feet of water, about 25 yards from the shore. The victim died an hour later at a hospital in Neenah.

The kids were among about 70 students from Milwaukee’s Roosevelt Middle School taking a field trip on their final day before summer vacation. Their trip was home was delayed so investigators could question them. Mauthe Lake is located near Campbellsport, and is part of the Kettle Moraine State Forest.