The U.S. Securities and Exchange Commission shuttered U.S. trading today and will hold a conference call at 18:00 ET to determine when trading may resume.

SEC chairman Harvey Pitt issued the following statement, “The commission has been, and is, in constant communication with each of our organized securities markets and exchanges. As a safety precaution while the tragic events of today are sorted out, the securities markets have decided not to open for trading today.”

The Federal Reserve announced that its system is open and operating. “The discount window is available to meet liquidity needs,” it said.

“We are continuing to monitor the situation, along with the securities markets, and investors should be assured that the disruption to normal trading patterns is a temporary phenomenon; trading will resume as soon as it is practicable to do so. We will keep the public advised,” said Pitt.