The Sydney Hih complex, presently being demolished, caught fire early Friday. The fire broke out about 1 a.m. and was elevated to a three-alarm blaze. By 3 a.m., the fire was under control. Credit: Andre Lewis

The Sydney Hih complex of buildings, which was partially demolished in recent days, caught fire early Friday.

A blaze that was eventually upgraded to a three-alarm fire was reported at 12:37 a.m., authorities said. A ladder truck was out front, and bystanders were observing the fire as smoke poured from the roof.

Two of the four buildings in the Sydney Hih complex have been demolished. One of the two remaining brick buildings has been partially demolished, and the main building, the Nicholas Senn Building, remains intact and is slated to come down.

When firefighters arrived, flames were visible from the fourth floor and the roof of the building at N. Old World 3rd St. and W. Juneau Ave.

Firefighters never entered the building, since it was scheduled to be demolished and some work had begun, said Battalion Chief Dale Schwark.

There was concern about the stability of the structure, he said.

"The whole roof was on fire when we got there. It's a four-story building. So the first thing we did was put water towers up. We had to keep our rigs back far enough and at the corners so in case it did collapse, nobody was injured. We just pounded water on it. There was really not a whole lot we could do. We knew that," Schwark said.

"We made the decision immediately that we were not going to go in. We didn't want to hurt anybody. Our concern was we didn't know what state of demolition it was in and we were concerned it might collapse from the beginning," Schwark said.

Firefighters were not able to immediately battle the blaze because some hydrants near the building were not operating correctly.

At least 75 firefighters battled the fire, which was brought under control about 2:30 a.m. Friday, Schwark said.

The cause of the fire has not been determined, but it is being investigated as suspicious, Schwark said.

Demolition of the Sydney Hih, once a home for 1970s counterculture and the alternative music scene of the '90s, began Aug. 9 after a protracted debate about whether the buildings should be preserved.

The demolition was halted Friday morning as investigators tried to determine the cause of the fire. But demolition resumed Friday afternoon.

Mike Johnson of the Journal Sentinel staff contributed to this report.