New York City ? It’s what New Yorkers like to say when they get a whiff of something funky: “Must be New Jersey.”

They said it again this week when a mysterious gas-like odor wafted across Manhattan and New Jersey. To which some indignant New Jerseyans said it’s the New Yorkers who are smelling up the joint.

The source of the stink remained a mystery Tuesday, as well as a rich source of juvenile jokes about New Jersey – and New York, too.

“You know what you call New York with a bad smell? New Jersey,” Jay Leno wisecracked. And Conan O’Brien killed with this: “Apparently, New Yorkers knew something was wrong because it smelled bad when they got OUT of their taxis.”

Garden State officials, tired of Jersey-bashing and industrial waste jokes, were quick to charge New Yorkers with prematurely blaming their long-time neighbors for the Monday morning stench that produced scores of 911 calls, disrupted transit service and sent a dozen people to the hospital.

“It looks an awful lot like jumping to conclusions,” said Lisa Jackson, New Jersey commissioner for environmental protection.