Prague/Washington - The US embassies in Prague and Tokyo on Thursday 18 December received letters containing suspicious white powder, the US Department of State announced last night.

The contents are being tested for presence of dangerous toxic substances. The sender remains unknown and the case is being investigated by the FBI.

A day earlier, similar envelopes with white powder were delivered to other US embassies in Europe, including Berlin, Copehagen, Dublin, Luxembourg, Rome, Tallinn and other capitals. Their contents turned out to be harmless. The letter delivered to the embassy in Madrid contained flour.

In 2001, several people in the US received envelopes by mail containing anthrax. Five people died after inhaling the poisonous powder. The attack was blamed on Bruce Ivins, an employee of a military laboratory for the research of biological weapons.

Earlier this month, the offices of 40 US governors received letters containing suspicious powder, all sent from a post office in Texas.