Excerpts from cbsnewschicago.com:

Firefighters spent nearly three hours battling a 3-11 alarm fire Thursday morning at a warehouse in the Back of the Yards neighborhood at the Evans Food Group processing plant near 41st and Halsted. 

Flames spread from the warehouse where it started to at least two connected buildings, and the roofs of all three buildings collapsed during the fire.

A worker at the plant said it is essentially a large kitchen that packs and ships food all over the country. McDonough said the warehouse stores pork products and grease that both helped fuel the blaze.

It was unclear how many employees were inside when the fire started but everyone got out safely prior to firefighters arriving.

The cause of the fire is under investigation.