December 21, 1888: The Jefferson Flour Mill explodes as naphtha (a flammable liquid hydrocarbon) refined at the Vacuum Oil Works leaks from an underground pipe into a sewer, igniting between State and Mill streets. The fire continued in the sewer, blowing man hole covers skyward and spouting flames for several hours. The accident resulted in five deaths.
Sources and further reading:
Rochester History (1988); vol 50, no 3, page 15