The air was thick with anxiety at the New York Stock Exchange on Monday as investigators began work at the site of where Malaysia Airlines Flight MH17 was downed last week in eastern Ukraine, veteran trader Art Cashin told CNBC.
"You can see the nervousness ... I think people don't believe that this will disappear as rapidly as it looked for a brief period on Friday to be," said Cashin, UBS' director of floor operations at the NYSE.
Pro-Russian rebels in eastern Ukraine are suspected of shooting down the jetliner with a missile, though Russian President Vladimir Putin has repeatedly denied Russia had any involvement.
Cashin spoke on "Squawk on the Street" just before President Barack Obama issued a statement outside the White House pressing Putin to be more cooperative.
Still, Cashin said investors fear tensions surrounding the Malaysia Airlines probe could grow.
"It's the idea of contagion: Is any of this going to spill out and effect other things?" he asked. "Don't forget that the S&P gets nearly half its earnings offshore. ... Globalization has finally taken hold. There aren't many places to hide these days."
—By CNBC's Drew Sandholm.