Andrew Gombert/European Pressphoto Agency

The legal onslaught continues for Bank of America.

On Tuesday, several homeowners filed suit in Federal District Court in Manhattan, seeking to block a proposed $8.5 billion settlement between Bank of America and major mortgage investors, including BlackRock, Pimco and the Federal Reserve Bank of New York. The suit says the deal fails to address widespread servicing problems and would actually speed up foreclosures.

In a separate new case, U.S. Bancorp, the trustee of a $1.75 billion mortgage pool originated by Countrywide Financial in 2005, sued to force Bank of America to buy back the underlying mortgages, arguing that the loans were made without proper documents and did not conform to underwriting standards.

“Soon after being sold to the trust, Countrywide’s loans began to become delinquent and default at a startling rate,” the complaint, filed Monday by U.S. Bancorp, said. “During the time period in which Countrywide originated the loans, it completely ignored its underwriting guidelines.” Bank of America acquired Countrywide, a subprime lending giant, in 2008.

The courtroom maneuvering on both fronts underscores the legal threats looming over Bank of America as a result of the collapse of the housing bubble and the disastrous acquisition of Countrywide, a $4 billion purchase that has already cost the bank more than $30 billion.

A wide variety of holders of mortgage bonds backed by defaulted home loans that were originated by Countrywide have been pushing Bank of America to repurchase the securities. The $8.5 billion agreement covers $424 billion in Countrywide mortgages that were packaged into mortgage bonds and sold to private investors.

The latest opposition to the $8.5 billion settlement coincided with a Tuesday deadline to file objections to the deal, which was negotiated in June by Bank of America, 22 large investors in soured mortgage-backed securities and Bank of New York Mellon, the trustee for those securities.

The Federal Housing Finance Agency, which oversees the mortgage giants Fannie Mae and Freddie Mac, on Tuesday filed a “conditional objection” to the $8.5 billion settlement, one day after the Federal Deposit Insurance Corporation made a similar move. Smaller investors have already filed legal actions opposing the deal, as has the New York state attorney general, Eric T. Schneiderman.

“There is a growing realization that this settlement needs more scrutiny,” said Keith Fleischman, the lawyer for the four homeowners in the suit. “It needs to address the housing crisis itself.”

A spokesman for Bank of America declined comment on both cases.

Lawyers for the National Consumer Law Center said in a report prepared as part of the case that the proposed settlement “will speed up foreclosures, perpetuate existing servicing abuses in the system, and undermine federal programs designed to stabilize the housing market.”

Bank of America had hoped the $8.5 billion settlement would finally put much of this potential liability behind it, but the challenges have raised investor fears that the ultimate cost of the settlement could rise sharply. Anxiety about the extent of Bank of America’s legal woes has also weighed on the bank’s stock, with some estimates suggesting the ultimate cost could be in the tens of billions.

In trading Tuesday, Bank of America shares closed down 3.2 percent at $8.12. They have fallen nearly 40 percent in 2011.

Still, the shares are well above the recent low of $6.30 they hit on Aug. 23. On Aug. 25, Warren E. Buffett agreed to invest $5 billion in the bank, reassuring investors who had worried about the bank’s underlying strength. And on Monday, the bank agreed to sell about half its stake in China Construction Bank, raising $8.3 billion and bolstering its Tier 1 capital position by $3.5 billion.