Sept. 8 (Bloomberg) -- Downey Financial Corp. and BankUnited Financial Corp. plunged today a week after regulators questioned the lenders' ability to absorb losses and a Raymond James analyst raised doubts about survival.

Downey tumbled 31 percent to $2.15 at 4:15 p.m. in New York Stock Exchange composite trading, the biggest drop since July. The stock had dropped more than 96 percent in 12 months. BankUnited fell 15 percent to $1.01 in Nasdaq Stock Market trading at 4 p.m. New York time.

Downey was among the biggest sellers of option adjustable- rate mortgages, which let borrowers defer part of the monthly payment and add it to the principal. BankUnited has more than $10 billion in home loans, and rising foreclosures in California and Florida led to more than $200 million in losses in the past three quarters.

``This is just another shot across the bow'' for BankUnited, said RBC Capital Markets analyst Gerard Cassidy.

BankUnited is no longer considered ``well-capitalized'' by regulators, the Coral Gables, Florida-based lender said in a regulatory filing Sept. 5. Regulators may restrict the lender's ability to accept deposits from brokers.

The shares of BankUnited were cut to ``underperform'' from ``market perform'' by Raymond James analyst Michael Rose, who said the company's ``ability to operate as a going concern remains in question, particularly in light of recent actions levied by regulators.''

Newport Beach, California-based Downey was ordered Sept. 5 to raise money by the end of the year, and must submit a long- term business plan to the Office of Thrift Supervision.

BankUnited

For BankUnited, ``one of the implications, and the most immediate, is the OTS can limit or prevent them from taking brokered deposits,'' said FTN Midwest Securities Corp. analyst Mark Muth in an interview today. Muth said that though BankUnited hasn't leaned on the deposits historically, they represented almost 10 percent of total deposits in August.

``It has clearly been a very important funding source for them,'' Muth said. ``If that goes away there is a potential liquidity issue.''

Thomas Prince, Downey's operating chief, has been interim chief executive officer since Daniel Rosenthal stepped down in July. Downey last month added former bank examiner Paul Homan to its board of directors, calling him an expert in ``troubled banks.''

To contact the reporter on this story: Linda Shen in New York at lshen21@bloomberg.net

Last Updated: September 8, 2008 16:26 EDT