CHICAGO (CBS) — It wasn’t just the looting that caused widespread devastation.

An unprecedented number of fires also swept across Chicago over the weekend. CBS 2 Investigator Dorothy Tucker has a look at the record number that left firefighters working around the clock.

Not since the Chicago Riots of 1968 has this city witnesses this many fires. The day after Dr. Martin Luther King, Jr. died, there were 36 major fires in one night.

This past weekend, in a little over 24 hour period, there were more than 80 fires.

They started Saturday night in the city’s central district downtown. CBS 2’s Jeremy Ross reported on a small but growing fire at a sports store on Michigan Avenue.

But by the time fire trucks maneuvered through the thousands of protesters, the store was engulfed in flames.

The scene played out over the next 30 hours into the wee hours of Monday morning. Fire fighters would respond to 85 calls. Each call represented retailers, who once had thriving business that were first ravaged by looters, then turned into infernos.

Fire fighters said looters seem to have a preference for beauty supply stores, Walgreens and liquor stores. One of the biggest fires was a beauty supply store on 79th and Damen.

Most of the fires were in communities on the West and South Side of Chicago. None of them has been fully investigated for a couple of reasons, according to fire officials.

One, at many, there were no police on the scene. Department protocol is not to conduct investigations without police present.

Two, it was too dangerous. The structures were unstable, not safe for firefighters or dogs to sniff for accelerants. Under the circumstances, the cause of most of the fires will never be determined.

Dorothy Tucker