More than 1000 firemen fought a persistent general alarm fire which destroyed a deserted seven-story Swift & Co. meat-packing plant in the Lechmere Square area yesterday.

Smoke from the fire, thought by some observers to be the largest in recent Boston history, was visible for ten miles, and dense smoke clowds snarled traffic in Harvard Square. Gusts of winds carried giant-sized embers, some of which were deposited, still burning, more than a mile from the blaze.

Reported at 3:20 p.m., the fire was thought to be under control by 4:30, but flames suddenly cut through the roof, drastically altering the situation. Sparks, which made a spectacular show as they descended on roof-tops, started a dozen minor fires, which were quickly extinguished.

An estimated 400 families were evacuated from a seven-block area as firemen drenched streets and houses with thousands of gallons of water. No serious injuries were reported, although several firemen were hospitalized briefly.

The fire was finally brought under control at 10:30 p.m., and mop-up operations will continue today.