The steep falloff in housing sales — which reached a 15-year low in July — highlights the degree to which the government has been propping up the housing market, and the two biggest pillars of that support system — Fannie Mae and Freddie Mac — are facing a crisis.

In Fla. this month, Fannie Mae auctioned off nearly 100 foreclosed properties. In Chicago, Freddie Mac was offering help to homeowners in distress, reports CBS News business correspondent Anthony Mason.

The two troubled mortgage giants seized by the government nearly two years ago now own or guarantee nearly 31 million home loans, 56 percent of all American mortgages, and they’re bleeding billions in losses.

Full story is available on CBS