U.S. stocks plunged into a deep sea of red Thursday, as economic fears at home and political concerns in Saudi Arabia weighed heavily on investor sentiment.

The Dow Jones industrial average tumbled 228 points, or 1.9 percent, to end at 11,985. It was the worst point drop in the Dow since Aug. 11.

All but one of the Dow’s 30 components closed lower in Thursday’s session. Energy and materials stocks were among the hardest hit, with Exxon Mobil, Caterpillar and Chevron all retreating 3 percent or more.

The S&P 500 lost 25 points, or 1.9 percent, to close at 1,295; and Nasdaq Composite lost 51 points, or 1.8 percent, to 2,701.

Thursday’s selling accelerated in the afternoon following news reports saying police in Saudi Arabia had fired shots or grenades at anti-government protestors. Protestors had reportedly scheduled a “Day of Rage” similar to the one that occurred in Egypt earlier this year.

Oil, which had been down as much as 3% earlier, erased the bulk of its losses following the reports.

Investors are worried the situation in oil-rich Saudi Arabia could deteriorate further, adding to the massive ongoing violence in Libya.

Saudi Arabia is a major oil producer, said Prudential Financial market strategist Quincy Krosby. “You don’t know where this Saudi issue is going to go but you do know it’s the country that could really cause supply disruptions.”

Bond prices rose as investors fled to the safety of government-backed investments.

Wave after wave of disappointing or disconcerting economic data has put heavy pressure on U.S. stocks. Before the open, investors got a wider U.S. trade gap and a worse-than-expected jobless benefit claims report.

“Now we’re back focusing on the economy,” said Marc Pado, chief equity strategist with Cantor Fitzgerald.