(Reuters) – Several bitcoin exchanges including the now-defunct Mt. Gox received subpoenas from Manhattan federal prosecutors this winter as they look into possible ties between the exchanges and the online drug market Silk Road, the Wall Street Journal reported on Monday, citing people familiar with the matter. The subpoenas to Mt. Gox demanded customer-transaction logs and materials related to solicitation of investors. The prosecutors and Federal Bureau of Investigation agents are examining whether the exchange and others like it may have processed transactions connected to Silk Road, the people said. The investigation was at an early stage and there were no conclusions yet on whether the exchanges were connected with Silk Road, one of the people familiar with the matter told the paper.