BY JEREMY TANNER wpix.com

6:19 p.m. EST, November 10, 2009
NEW YORK, N.Y. (WPIX)—
Two suspicious letters containing white powder arrived at the United Kingdom and German UN missions Tuesday, but both are believed to be just the latest development in a hoax, officials announced.

Initial tests of the powder have not revealed any harmful substances, but authorities are taking precautionary measures, decontaminating areas within the German mission and sending the powder to a local lab for more testing.

The UK mission is the latest to receive a suspicious letter, while the German mission received a similar one Tuesday morning. The UN missions of Uzbekistan, Austria and France all received suspicious packages with harmless white powder Monday.

"It turns out that the substance was nothing harmful. But we're certainly investigating," Mayor Bloomberg told reporters Tuesday, "Anybody that thinks it's a joke is making a very bad mistake. If we apprehend you, you're going to face criminal charges."

The latest letter arrived Tuesday morning on the 21st floor of the German mission and reportedly contained a suspicious message that has yet to be released.

All of the letters are reported to have a Dallas postmark, but the return addresses are different. Authorities are still trying to confirm that the letters were actually sent from Dallas.

A message with "AL-QUAIDA" written in block letters was included in each of Monday's letters, but no demands were made.