It's quite possible it will never be known what caused the Friday fire that destroyed the Interstate Batteries building in downtown Bismarck.

"I don't even know what we'll be able to find in there," said Rob Carlson, an acting battalion chief for the Bismarck Fire Department, on Saturday.

The build-up of ice in the building, located at 901 E. Main Ave., was extensive after an all-day fire fight by 42 of the department's 54 firefighters.

The city fire marshal will "probably determine it can't be investigated," Carlson said.