The stock market had its worst day in nearly a decade Monday as fears rise about coronavirus and Saudi Arabia and Russia clash over crude oil prices.

The S&P declined by 7% in the first five minutes of trading Monday, leading to a circuit breaker, which halted trade for 15 minutes to avoid stocks falling through the floor. The market is on track for its worst day since August 2011, when it lost $1 trillion.

The decline comes as the Coronavirus continues to spread in the U.S. Two members of Congress announced Thursday that they are self-quarantining after coming coming in contact with someone who has the virus. Republican Sen. Ted Cruz of Texas and Rep. Paul Gosar of Arizona were both exposed to the virus during last month’s Conservative Political Action Conference (CPAC) in Maryland. (RELATED: Here’s How To Prepare For The Coronavirus)

President Donald Trump blamed market troubles on the oil dispute between Saudi Arabia and Russia. Oil prices plunged 30% Sunday night amid the dispute.

“Saudi Arabia and Russia are arguing over the price and flow of oil,” Trump tweeted Monday morning. “That, and the Fake News, is the reason for the market drop!”