By Emily Flitter NEW YORK (Reuters) – Manhattan U.S. Attorney Preet Bharara has sent subpoenas to Mt. Gox, other bitcoin exchanges, and businesses that deal in bitcoin to seek information on how they handled recent cyber attacks, a source familiar with the probe said on Wednesday. At least three exchanges were forced to halt withdrawals of bitcoins on February 7, including Mt. Gox, which was the largest at the time. Mt. Gox never resumed service before going dormant on Tuesday, leaving customers unable to recover their funds. As there is a lot of speculation regarding Mt Gox and its future, I would like to use this opportunity to reassure everyone that I am still in Japan, and working very hard with the support of different parties to find a solution to our recent issues, Karpeles said in a statement posted on the Mt. Gox website.