A manhole in midtown erupted in flames and black smoke a Monday afternoon, snarling traffic and resulting in the temporary evacuation of 1,500 workers from 140 W. 51st St., said officials.

Extreme weather - a contributing cause of so many winter fires - was likely a factor in yesterday's blaze, which took 60 firefighters more than two hours to quell, said Con Ed spokesman Bob McGee. "After a snow storm and a lot of salt is applied to the streets, it melts and washes into the (underground) vaults," eroding insulation that surrounds live wires, explained Con Ed spokesman Bob McGee.

Firefighters were called to the blaze -- near the Time Life Building -- at 2:11 p.m. "We had it contained, but it didn't shut down," until Con Ed managed to cut the power to the affected wires at 4:07, said an FDNY spokesman. The fire was snuffed out 14 minutes later, he said. Workers were evacuated due to concerns about heightened carbon monoxide levels, and one person who reported respiratory irritation declined treatment, said the FDNY.

Con Ed service to the surrounding areas was unaffected, McGee said.