Flames outside of flame chamber

I have a Utica steam boiler. The other day thr heat would not turn on. Checker boiler and saw that the switch mounted on the wall of the fire box about 6 inches above the flame tubes was melted. By passed the melted switch to see what was happening and I have flames coming out the hole for the gas tubes. I pulled the tubes out (except for the one that the pilot is attached to) and wire brushed the vent holes thinking they may have gotten blocked but that did not help.

Any other suggestions?

Thank You in advance