WASHINGTON - December 23, 2010 - As the housing market came crashing down in 2008, the giant mortgage company Fannie Mae took an unprecedented step to help tackle the rising tide of foreclosures. It named an exclusive group of law firms that would help rapidly carry out the unsavory task of filing legal paperwork to remove homeowners from their homes.

Today, problems with documents handled by firms on Fannie's list - and a similar one created by its smaller rival Freddie Mac - are at the heart of federal and state probes over faulty foreclosure practices that now threaten to further undermine the housing market.

Fannie and Freddie, the largest mortgage companies, shaped the practices being challenged in courtrooms around the country. They picked law firms that could foreclose fast and paid them based on how many foreclosures they could process. Speed was essential because delays cost the companies money - and, after they were taken over by the government two years ago, meant losses for taxpayers, too.

Not only did the companies urge swift foreclosures, but in at least one case Fannie executives also greenlighted working with a firm that they knew firsthand had engaged in legally questionable practices, according to documents and interviews with lawyers and industry officials.