Lawmakers are working to get to the bottom of another facet of the financial crisis -- the housing crisis.

Four former CEO's of the mortgage giants Freddie Mac and Fannie Mae were on the defense before a congressional committee Tuesday. Congress is digging in to determine how much blame should be placed on the two firms.

The CEO's are accused of ignoring internal memos that warned both firms they were loaning too much money to risky borrowers.

The CEO's claim they were pressured into taking on these loans, but some congressmen say they need to accept some responsibility.

"Your testimony says you're not accepting any blame for this at all,” said Representative Darrell Issa. “You're either standing behind the mandate of the Congress, or the mandate of your stockholders, perhaps the mandate of your bonus-packages and you're telling us, in fact, 'everyone was doing it'."

Freddie Mac and Fannie Mae were seized by the government three months ago after nearly collapsing in the wake of billions of dollars of losses on mortgages.