It was the second manhole incident involving the beleaguered utility in the past two days.
Last night's problem started at around 6:30 p.m., when "a smoldering fire" beneath Hull Street in Brownsville caused several manholes to "pop," said Deputy Fire Chief David Jakubowski.
The fire sent carbon monoxide flowing into homes on Hull between Thomas Boyland Street and Rockaway Avenue.
Officials evacuated more than 100 residents.
Some waited in buses and others were taken to a local school.
Jakubowski said carbon-monoxide levels in some homes were as high as 2,000 parts per million. Evacuation is mandatory at 100 per million.
Chris Olert, a spokesman for Con Edison, said the incident was likely caused by wires burning out, possibly due to a weather-related mixture of rock salt and water.
Officials said residents were expected to be allowed back in their homes by early today.
Neighbors were furious, charging that Con Ed was slow to respond.
"You don't make a payment and they're ready to shut you off. You call them with a problem, and they don't show up or they take a long time to come," said Kevin Brown. "You'll pass out by the time they get here."
On Tuesday night, a firefighter was injured in the East Village while battling a blaze in a Con Edison manhole on Avenue B, just three blocks from where a woman was killed by stray voltage in January.
