Three people crawled through the windows of their SUV to safety just minutes before the vehicle broke completely through the ice of Big Lake in Sherburne County on Sunday and sank to the bottom, 25 feet below.

Steven Bergquist, 45, of Big Lake, Natalie Muehring, 46, of Albertville, and Bergquist's 12-year-old son escaped without injury after the rear portion of their 2003 Chevy Trailblazer broke through the ice, about 100 yards form the lake's north shoreline, the Sherburne County Sheriff's Office said Monday. They were traveling to their fish house on approximately seven inches of ice, officials said.

Efforts to remove the vehicle continued Monday.

This past weekend's fishing contest on Big Lake was canceled because of thin ice, said Sherburne County Sheriff's Capt. Steve Doran.

Also Monday, Sheriff Joel Brott said he is closing Big Lake and Mitchell Lake to cars, trucks and SUVs effective Thursday. Brott cited unpredictable lake ice conditions because of warm weather this winter. The Sheriff's Office noted that yards from where the SUV broke through on Sunday, the ice was a foot thick, showing high variability in thickness over a relatively short distance.

The dangers of thin ice have been sounded repeatedly in the Twin Cities. Last week, the Hennepin County Sheriff's Office banned vehicles on all county lakes. In Sherburne County, an ATV broke through the ice on Eagle Lake a month ago. The county also has received reports of fish houses and snowmobiles cracking through thin ice, Doran said.