Federal investigators have expanded their broad investigation into the collapse of the subprime mortgage market to include Fannie Mae, Freddie Mac, Lehman Brothers and AIG – four companies at the heart of the current market turmoil.

Enforcement officials are under growing pressure to hold companies and individuals responsible for the worst financial crisis since the Great Depression.

In recent weeks, various regulators, both at the federal and state level, have been revealing the existence of investigations into the collapse of the subprime mortgage market and allegations of market manipulation.

The inquires into Fannie, Freddie, Lehman and AIG are part of a broader probe and still at early stages, according to people familiar with the matter.

Financial Times