Six of the nation’s largest banks have consistently failed to aggressively market and maintain foreclosed homes in communities of color, according to the results of a nine-month long investigation released Tuesday.

The investigation by the National Fair Housing Alliance, a Washington, D.C.-based nonprofit that investigates, tracks and researches housing discrimination, studied the way banks market and maintain vacant foreclosed homes in nine metro areas and found “overwhelming” and “troubling“ evidence that banks consistently market and maintain foreclosed homes in the nation’s predominantly white neighborhoods differently. The findings constitute a violation of federal civil rights law and show that blacks and Latinos are unfairly burdened with one of the worst aspects of the nation's housing crisis, alliance officials said.

“This is not about income. It is about race. These were consistent patterns in low-income communities, middle-income communities and upper-income neighborhoods,” said Shanna Smith, the alliance’s president and CEO. “And besides that, nobody, regardless of their income, wants to live next door to a property that is filled with trash and overgrown weeds that grow and foster rodents. No one deserves that.”

Investigators from the alliance, which completed its investigation in February, examined conditions at 1,000 bank-owned properties in ZIP codes with elevated foreclosure rates. The homes, often referred to as REO or real estate-owned properties, were ostensibly for sale after a bank reclaimed them in a foreclosure.

Bank-owned homes in communities of color were 42 percent more likely to have visible maintenance problems such as overgrown grass, hanging gutters, and damaged eaves or siding than those in comparable white neighborhoods. Foreclosed homes in mostly black and Latino neighborhoods were 34 percent more likely to be littered with trash and debris, and 82 percent more likely than bank-owned properties in white communities to have broken or boarded-up windows.

Vacant and foreclosed bank-owned homes in white neighborhoods were 33 percent more likely to be designated with professional real estate signs that were visible from the street. Homes in black and Latino neighborhoods had signs made of construction paper or cardboard, or had no for-sale signs at all.

It is difficult to identify the precise number of bank-owned properties in the United States. In mid-2011, there were at least 500,000 vacant bank-owned homes and another 2 million foreclosures expected, a January Federal Reserve analysis found.

What is clear is that the nation’s housing crisis already has created so many vacant, foreclosed and bank-owned homes that how quickly these properties sell, what they sell for and to whom they sell will play a major role in what becomes of the housing market and the broader economy’s health.

Differences in the way banks maintain and market vacant foreclosed homes in mostly white neighborhoods and communities where black and Latino families live, may be deepening the nation’s housing crisis, damaging the property tax bases on which most communities depend and leaving many black and Latino homeowners stranded in increasingly blighted neighborhoods, according to the investigation.

But Bob Davis, executive vice president for mortgage policy for the banking-industry trade group American Bankers Association, said maintain properties does not depend on ZIP codes.

“Banks are in the business of lending and strive to sell foreclosures as quickly as possible," he said in an emailed statement. "Banks take care of these houses to preserve their collateral regardless of where the property is located. Banks operate and are examined under fair lending and fair housing laws to ensure equal treatment across all communities."

The American Mortgage Bankers Association did not respond to requests for comment about the alliance’s report Wednesday.

The alliance declined to name the six banks that owned the majority of homes included in the investigation. It plans to file a series of administrative complaints with the Department of Housing and Urban Affairs beginning next week in which the banks will be named.

Administrative complaints can lead to a formal civil rights investigation led by HUD or similar state agencies, negotiations, or a court case and fines. Victims of housing discrimination also can be awarded monetary damages plus compensation for pain, suffering and other experiences.

Investigators working with the alliance examined homes in the Atlanta, Oakland, Dallas, Miami, Dayton, Washington, D.C., Baltimore, Philadelphia and Phoenix areas. They examined each REO property in select ZIP codes with elevated rates of foreclosure. The alliance is one of several nonprofit groups that receive federal funds to conduct fair housing investigations and secret-shopper-style housing tests.