First Republic Bank's shares jumped nearly 22% before trading was halted Thursday after several large banks were said to be in talks to deposit billions of dollars to salvage the embattled lender, three sources with knowledge of the matter said.

The banks are set to deposit $29 billion, according to one of the sources.

This follows a round of financing on Sunday raised through JPMorgan Chase & Co., which gave First Republic access to a total of $70 billion in funds, but failed to calm investors as worries of a contagion deepened in the wake of two large-scale collapses in the banking industry.

Four major banks including JPMorgan, Citigroup Inc., Bank of America Corp. and Wells Fargo & Co. are part of the rescue, one of the sources said.

The effort was initiated by banks but had strong backing and encouragement from the government, according to a second source with knowledge of the matter.

Eleven banks were involved, and the rescue plan is supported by U.S. regulators, one of the sources said.

Founded in 1985, First Republic had $212 billion in assets and $176.4 billion in deposits as of the end of last year, according to its annual report.

About 70% of its deposits are uninsured, above the median of 55% for medium-sized banks and the third highest in the group after Silicon Valley Bank and Signature Bank, according to a Bank of America note.

Earlier on Thursday, Reuters reported PacWest Corp. is also in talks about a liquidity boost with investment firm Atlas SP Partners.

Banks including JPMorgan and Morgan Stanley are in talks with First Republic for a potential deal that could bolster its finances, several media reports said Thursday.

The banks are set to deposit $30 billion with First Republic in a concerted effort by the U.S. government to rescue the struggling lender, Bloomberg News reported on Thursday, citing people with knowledge of the matter.