The investigation has been turned over to police, officials said, after it was determined someone may have started it around 4:20 a.m., in a storage shed near Cafe Brauer, 2021 N. Stockton Dr.

Sources on the scene told CBS News Chicago that a firefighter who responded to the fire was taken to Illinois Masonic Hospital with minor injuries.

The fire appeared to have started near the side of the building where the ballroom and patio are located. Cafe Brauer backs up to the South Pond and nature area portion of the zoo. The cause of the fire is under investigation.

Crews put out a fire that started outside a popular café and event space near Lincoln Park Zoo on Friday morning.A group of propane tanks reportedly caught fire around 5 a.m. outside of Café Brauer, the historic party space located at 2021 N.