The nation's key mortgage agencies and fed bank shuttered their doors Monday as Hurricane Sandy threatened the East Coast.

The Federal Reserve Bank of New York opened Monday morning, but shut down its trading of agency mortgage-backed securities as Manhattan braced for Hurricane Sandy.

The Fed bank said financial market closures and market conditions made it essential for the bank to change operations of the System Open Market Account.

Most trading markets are either closed or closing.

A Treasury securities sale scheduled for Monday will still take place, but the settlement will not occur until Wednesday, pushing the conclusion of the transaction back another day. Treasury securities purchases scheduled for tomorrow have been postponed and will be rescheduled later in the week, with Wednesday being the most likely re-start date.

The Federal Housing Finance Agency also announced it would be closed Monday, along with the government-sponsored entities, Fannie Mae and Freddie Mac. Freddie did say critical functions are operating and lenders and investors can still do business. The GSE also had a reference bill move forward, but employees overall are staying home to prepare for the storm.