The state fire marshal was in Decorah Thursday to investigate the cause of a fire early Wednesday morning that caused extensive damage to Cho Sun Restaurant in Decorah.

However, due to sub-zero temperatures, the fire scene needed to be "thawed out" to complete the investigation, according to Decorah Fire Chief Mike Ashbacher.

"It was too frozen," he said.

A heater was used over the weekend to thaw it out.

The state fire marshal obtained "preliminary information" from the scene Thursday and was scheduled to return today, Tuesday, for a complete investigation, Ashbacher said. Insurance company investigators also will be going through the building.

Restaurant owner Nika Lee said she plans to reopen, but she doesn't know when due to the amount of damage sustained.

The Decorah Fire Department responded to the fire at about 1:36 a.m. Wednesday. When firefighters arrived, there was intense damage to the west side of the building. Smoke, heat and water damage was reported to the rest of the building.

The Decorah Fire Department was assisted by the Calmar and Ossian Fire Departments, the Winneshiek Medical Center Ambulance Service, the Decorah Police Department, Winneshiek County Sheriff's Department, Alliant Energy and Black Hills Energy.