The Rockford Fire Department continues to investigate the Charles Street fire among a number of others.
13 News has learned the Charles Street fire is one of 37 unsolved, active investigations with Rockford Fire.
The vacant building burned down last month. The cause of the fire is still unknown.
Rockford Fire officials said a case remains open when they have reason to believe the fire could have been intentionally set.
In all, there have been 505 fires in the city this year. Of those cases, 201 had a fire investigator assigned to it. The rest were cut and dry investigations, said officials. Thirty-seven of those cases remain open.
Rockford Fire officials said there is no statute of limitation on arson, so any case can be reopened at any time if new evidence surfaces.