From the New Scientist:

The DNA sequence of the anthrax sent through the US mail in 2001 has been revealed and confirms suspicions that the bacteria originally came from a US military laboratory.

The data released uses codenames for the reference strains against which the attack strain was compared. But New Scientist can reveal that the two reference strains that appear identical to the attack strain most likely originated at the US Army Medical Research Institute for Infectious Diseases at Fort Detrick (USAMRIID), Maryland.

The new work also shows that substantial genetic differences can emerge in two samples of an anthrax culture separated for only three years. This means the attacker's anthrax was not separated from its ancestors at USAMRIID for many generations.

Full article:  http://www.newscientist.com/news/news.jsp?id=ns99992265

Meanwhile, at the BBC:

US scientists are closer to knowing the sources of last year's anthrax attacks.
They have found a "fingerprint" series of genetic markers which can be used to tell the difference between very similar strains of the bacterium.

...

The identification of "signatures" means it could eventually be possible to work out where the anthrax used in the 2001 attacks came from.

Full article:  http://news.bbc.co.uk/hi/english/sci/tech/newsid_1977000/1977894.stm