All the news networks are covering what appears to be a gas-like odor spreading through half of Manhattan.

Good updates at Hotair and in the comments at Gothamist.

Some additional info:

NYPD Scanners are reporting calls of bad gas odors coming from Staten Island, near the Staten Island Expressway but nothing has been confirmed as of yet.

New York City Mayor Bloomberg says that while an odor has been detected that is similar to a chemical placed in natural gas, no evidence of natural gas has been picked up by the city's numerous air sensors.