Five UN missions in NY get white powder letters

* Austria, France, UK, Germany, Uzbekistan targeted

* Initial results show powder was harmless - diplomats (Adds British mission also getting white powder letter)

UNITED NATIONS, Nov 10 (Reuters) - Police are investigating letters containing white powder that were sent to five U.N. missions in New York City, but diplomats from the affected countries said on Tuesday that the material was harmless.

The U.N. missions of Austria, France, Germany and Uzbekistan received letters with an unidentified white powder on Monday.

Britain's U.N. mission in Manhattan also received a letter containing white powder on Tuesday and authorities were decontaminating the office where it was found, a British diplomat in New York told Reuters.

The New York Police Department has said that it had already decontaminated 40 people as a precaution.

"The material is being examined by the authorities, and the preliminary finding we've received is that it was not dangerous," Austrian U.N. Ambassador Thomas Mayr-Harting said at U.N. headquarters.

U.S. authorities have been on alert for mail with white powder in it since 2001, when envelopes laced with anthrax were sent to media outlets and U.S. lawmakers, killing five people.

French Ambassador Gerard Araud said the decontamination of his mission went on until after 3 a.m./0800 GMT. He said the letter was postmarked in Dallas, as were the letters received by the Austrian and German missions.

It was not immediately clear where the other two letters were sent from. Officials at the German and Uzbek missions said operations were back to normal at their offices and the people who opened the letters had returned to work.

Mayr-Harting declined to comment on the contents of the letter that accompanied the powder. A police spokesman also said he could not confirm media reports that the letters referred to al Qaeda.

French, German and Austrian officials said they had no idea why their missions had been targeted. An Uzbekistan embassy official did not offer details. (Reporting by Louis Charbonneau; Editing by Eric Walsh)