NEW YORK - Stock markets tumbled on Wednesday, as investors’ fears over the health of the banking industry resurfaced and spread around the world, undoing a rally on Tuesday when the panic appeared to pause.

On Wall Street, the S&P 500 fell 1.6 percent at the open of trading, reversing all of the previous day’s gains. European markets were also hard hit, with stocks of many of the region’s biggest banks falling sharply, as anxiety persists about the fallout from the collapse of Silicon Valley Bank and Signature Bank, which were seized by regulators after suffering devastating runs on deposits.

The catalyst for the day’s turmoil appeared to be Credit Suisse, the mistake-prone Swiss bank that has struggled for years to turn around its fortunes, with customers steadily shifting their assets to rival banks. It recorded the most eye-catching decline, with its shares losing roughly 30 percent, setting yet another record low. On Wednesday, the bank’s largest shareholder, Saudi National Bank, ruled out providing more money for Credit Suisse as it struggles with its latest turnaround plan.

The banks’ bond prices plummeted and the cost of insuring the bank’s debt against a possible default soared. S&P Global Ratings said on Tuesday that European banks had little exposure to Silicon Valley Bank or Signature Bank, nor did they view any European banks as being exposed to the same risks. “That said, we are mindful that SVB’s failure has shaken confidence,” analysts at the rating agency said.