DULUTH – A fire that broke out Saturday morning caused part of the roof of a three-story building downtown to collapse.

The owner of the property at 118 E. 1st St. told the Duluth Fire Department that the building was being used as a warehouse, according to city spokeswoman Kate Van Daele. It previously housed an antique shop.

Van Daele said officials from the fire marshal's office called the building "a complete loss," estimating that it sustained $1 million in damages.

The blaze broke out around 9:30 a.m. Saturday, and firefighters were still working to quell flames in late afternoon. First responders believe the fire started in the eastern corner of the building's top floor.

"Crews arrived on scene and immediately went on the defensive," Van Daele said. "They weren't able to get into the building because of how big the flames were."

She added that fire officials did not believe anyone was inside the building.

The city blocked off a portion of 1st Street while responding to the blaze, which created plumes of smoke that caught the attention of those living farther up Duluth's hillside.

Van Daele said Saturday that officials had not determined the cause of the fire, which was under investigation by the fire marshal's office.

Authorities are asking for help identifying people who were near the scene Saturday morning. Anyone with information is asked to call the fire marshal's office at 218-730-4380.

Another fire on the same block burned the historic Pastoret Terrace property Nov. 1. The cause of that blaze also remains under investigation.

Katie Galioto • 612-673-4478