ST. CLOUD, Minn. — Officials in St. Cloud said Tuesday they don't know yet what caused a fire that destroyed a historic downtown bar.

St. Cloud Fire Chief Dean Wrobbel said the fire started in the basement of the Press Bar and spread throughout the walls of the building.

"In these old buildings, especially for the time that it started and had a head start on us, we could not get down to the fire. We were in the building for about 45 minutes trying to find the seed of the fire, we could hear it in the walls and we just could not get to it," Wrobbel told reporters.

The state Fire Marshal's Office was on the scene Tuesday. Investigators are expected to spend much of the day going through the rubble.

"We take a rectangular shape of the basement and work in quadrants. We will continue to go in today and look at material loss, fire patterns, which direction the fire was traveling. All those things are still there, it's just going to take some time to discover them," Post said.

Post said depending on what investigators find Tuesday, the investigation could take a few days to several weeks to determine the cause of the fire, WJON-AM reported.

The fire broke out Monday morning. By that afternoon, the entire building had been leveled. Rubble continued to smolder Tuesday.

The Press Bar dated back to 1942.