U.S. Treasury Secretary Janet Yellen said she was working with regulators to respond to the collapse of Silicon Valley Bank but ruled out a bailout, as fears of a broader fallout across the banking sector deepened.

Startup-focused lender SVB Financial Groupon Friday became the largest bank to fail since the 2008 financial crisis, roiling markets and leaving billions of dollars belonging to companies and investors stranded. Concerns grew that if regulators did not find a buyer to protect uninsured deposits, distress could ripple through U.S. regional banks.

The Federal Deposit Insurance Corporation (FDIC), which was appointed receiver, was trying to find another bank over the weekend that was willing to merge with Silicon Valley Bank, people familiar with the matter said on Friday.

Yellen on Sunday said she was working closely with banking regulators to protect depositors, but ruled out a government bailout.

“We want to make sure that the troubles that exist at one bank don’t create contagion to others that are sound,” Yellen told the CBS News Sunday Morning show.

“Let me be clear that during the financial crisis, there were investors and owners of systemic large banks that were bailed out…and the reforms that have been put in place means we are not going to do that again,” she said.

U.S. House of Representatives Speaker Kevin McCarthy told Fox News’ Sunday Morning Futures program that the Biden administration and the Federal Reserve were working to come up with announcement before the markets open, without specifying any details.

Reuters was unable to determine whether a deal for the bank was forthcoming. Some industry executives said such a deal would be sizeable for any bank and would likely require regulators to give special guarantees and make other allowances for any buyer.

With $209 billion in assets, the Santa Clara, California-based lender was the 16th largest U.S. bank, making the list of potential buyers who could pull off a deal over a weekend relatively short, they said on condition of anonymity because the situation is in flux.

The U.S. Federal Reserve and the FDIC were weighing the creation of a fund that would allow regulators to backstop more deposits at banks that run into trouble, Bloomberg reported.

Regulators discussed the new special vehicle in conversations with banking executives and hoped such a measure would reassure depositors and help contain any panic, the report said.

However, it was not clear if regulators would have political support to throw a lifeline to the bank, which catered to Silicon Valley startups and investors.

The Fed and FDIC did not immediately respond to a request for comment.

The White House said on Saturday that President Joe Biden had spoken with California Governor Gavin Newsom about the bank and efforts to address the situation.

“Everyone is working with FDIC to stabilize the situation as quickly as possible,” Newsom said on Saturday.

SPOTLIGHT ON OTHER BANKS

Some analysts and prominent investors warned that without a resolution by Monday, other banks could come under pressure if people worried about their deposits.

“The good news is it is unlikely an SVB-style bankruptcy will extend to the large banks,” risk and financial advisory firm Kroll said in a research note.

However, small community banks could face issues and the risk is “much higher if uninsured depositors of SVB aren’t made whole and have to take a haircut on their deposits,” Kroll added.

Silicon Valley Bank had an unusually high level of deposits that were not covered by the FDIC’s guarantees, which are capped at $250,000.

Billionaire hedge fund manager Bill Ackman said in a tweet on Saturday that failure to protect all depositors could lead to the withdrawal of uninsured deposits from other institutions as well.

“These withdrawals will drain liquidity from community, regional and other banks and begin the destruction of these important institutions,” Ackman, who said he does not have direct exposure, warned.

Kyle Bass, founder and chief investment officer of Hayman Capital Management, who also does not have exposure to SVB, told Reuters that the Fed needed to “arrange a marriage” for SVB by Sunday evening, before markets opened in Asia.

“And they’ve got to assure depositors that they will be paid in full because of this merger, and restore stability in the banking system,” he added.

Regional and smaller bank shares were hit hard on Friday. The S&P 500 regional banks index dropped 4.3%, bringing its loss for the week to 18%, its worst week since 2009.

Signature Bank dropped about 23%, while San Francisco-based First Republic Bank fell 15%. Western Alliance Bancorp tumbled 21% and PacWest Bancorp dropped 38% after those stocks were halted several times due to volatility. Charles Schwab Corp slumped more than 11%.

Signature Bank, First Republic Bank, PacWest Bank and Charles Schwab did not immediately respond to requests for comment. Western Alliance Bank declined to comment.

Some banks could look to preemptively raise capital to fortify their balance sheets or try to strike deals of their own, industry executives said.

When IndyMac and Washington Mutual collapsed in 2008, the FDIC found other firms to take on the assets and keep deposits intact. If no buyer is found for SVB, uninsured depositors will probably be left with a portion of whatever funds the FDIC can raise selling off the bank’s assets.

GLOBAL DOMINOES

In the UK, where SVB has a local subsidiary, finance minister Jeremy Hunt said on Sunday he was working with Prime Minister Rishi Sunak and the Bank of England to “avoid or minimize damage” resulting from the chaos that has engulfed the lender.

“We’ve been working at pace over the weekend, through the night,” Hunt told Sky News. “We will bring forward very soon plans to make sure people are able to meet their cashflow requirements to pay their staff.”

More than 250 UK tech firm executives signed a letter addressed to Hunt on Saturday calling for government intervention, a copy seen by Reuters shows.

Advisory firm Rothschild & Co is exploring options for Silicon Valley Bank UK Limited as insolvency looms, two people familiar with the discussions told Reuters on Saturday. The BoE has said it is seeking a court order to place the UK arm into an insolvency procedure.

Some experts, however, see the fallout from the latest collapse as limited.

“We do not see this as the start of a broader threat to the safety and soundness of the banking system,” TD Cowen analyst Jaret Seiberg said on Friday. “Silicon Valley had a unique business model that was less dependent on retail deposits than a traditional bank.”