About 200 early-season ice fishers were caught by surprise and stranded in a Minnesota lake when the frozen slab under their feet broke free and drifted into open water -- triggering a complex rescue operation.

A member of the group called emergency services Monday when they realized the people ice fishing -- a popular winter sport in the northern US state known as the Land of 10,000 Lakes -- were slowly drifting away from the shoreline of Upper Red Lake, local police said on Facebook.

"The Beltrami County Sheriff's Office and other first responders arrived on scene and discovered a large portion of the ice with up to 30 yards (27 meters) of open water stranding the fishermen," Chief Deputy Jarrett Walton said in a statement.

Some of the group had not even realized the ice floe had snapped free. But "due to the urgent nature of getting people off the ice," Beltrami County sent out an alert to the fishermen's cellphones to notify them they would soon be rescued in an emergency evacuation.

The alert "allowed notifications to be sent to cell phones of those who are not enrolled in the local notification system and provided GPS coordinates of the evacuation site," the sheriff's department said.

It took over three hours to complete the evacuate from the ice.

"A number of apparatus were deployed including airboats, water rescue boats, ATVs, drones and a temporary bridge," the sheriff's department said.

It also warned other local fisherman to use "extreme caution" on unsteady ice.

"The Beltrami County Sheriff's Office reminds those who are thinking of heading on the ice that early season ice is very unpredictable," the statement said.