Wall Street losses snowballed Thursday, with the Dow Jones industrial average plummeting 10 percent, even after the Federal Reserve took the highly unusual step of injecting more money into the bond market to stabilize the financial systems amid growing panic about the coronavirus and its stranglehold on the economy.

The Dow skidded 2,352.60 points for its worst finish since 1987. The Standard & Poor’s 500 index plunged 9.5 percent as stocks spiraled further into a bear market — which signifies a 20 percent decline from an all-time high.

The New York Fed will pump $1.5 trillion into the short-term lending markets that banks use to lend to each other on Thursday and Friday. The central bank also announced it will buy $60 billion worth of Treasury bonds for the next month (March 13 through April 13) to help keep that market functioning appropriately. Earlier this week, investors reported problems trading in U.S. government bonds. These irregularities echoed the types of freezes seen during the 2008 financial crisis, and the Fed appeared to want to act quickly to stop them.

The Fed’s action brought some relief to Wall Street on an especially tumultuous day that forced a brief cessation of trading. The sell-off began shortly after the open, following President Trump’s announcement that he would restrict nearly all travel from Europe for 30 days to stem the spread of the coronavirus. The Dow tumbled nearly 1,700 points, but it was the S&P 500’s 7 percent slide that triggered the so-called circuit breaker — a 15-minute break to stop the market free-fall and give traders time to recalibrate.

But by day’s end, the countermeasures did little to break the cycle. The Dow closed at 21,200.62, down 10 percent. The S&P 500 skidded 9.5 percent and the tech-heavy Nasdaq fell 9.4 percent.

Thursday’s dive follows the frenetic pace on Wall Street all week and comes a day after the Dow morphed into a bear market. The S&P 500 triggered the first circuit breaker of the week on Monday after falling 7 percent early into the session. By the end of day, it had shed 7.6 percent and the Dow had lost a stunning 2,014 points, or 7.8 percent. The markets bounced back Tuesday, posting across-the-board gains, only to recoil Wednesday after the World Health Organization declared the coronavirus a pandemic. The Dow cratered nearly 1,500 points to fall into a bear market.