UNITED NATIONS - A suspicious envelope containing white powder whose discovery led to the closure of the UN main dining room and staff cafeteria appears to be harmless but is still being analysed, a UN spokesman said on Friday. Spokesman Martin Nesirky said preliminary results indicated that the envelope contained a non-toxic substance. The United Nations is still awaiting final laboratory results on the non-organic substance and the cafeteria would remain closed, he said in a statement. The United Nations closed its main dining room and staff cafeteria on Thursday after the envelope was found. UN Security Staff called in New York City authorities to help investigate the contents of the envelope.