(CNBC) — Stocks plunged sharply Thursday, with the Dow down more than 500 points, in the biggest selloff since May 2010. All three major averages tumbled into negative territory for the year as investors were rattled over an intensifying global economic slowdown and ahead of the widely-followed monthly unemployment report.

“We’re not steering this bus — it’s all coming from Europe,” Art Cashin, director of floor operations at UBS Financial Services told CNBC. “We’re hearing reports of funds drawing out of European banks and we’re pretty close to something that might turn ugly.”

“It may translate into a strain on the financials system and earnings on the multinationals, which have been carrying the load for Wall Street,” Cashin added.