The American consulate in Thessaloniki was closed to the public yesterday and security was stepped up after Greek police on Thursday received a phone threat warning of an imminent attack. Police officers carefully investigated the eight-story office building at 43 Tsimiski Street on whose seventh floor the consulate has been housed since 1999, but found nothing suspicious. However, additional guards were assigned to the building, and local police patrols were increased. A senior Thessaloniki police officer described the threat as «anything from very serious to plain ridiculous.» The Foreign Ministry notified the US Embassy in Athens, which in turn told the State Department. Officials in Washington decided to close the consulate, to be on the safe side. It will reopen on Tuesday, as Monday is a US public holiday. During the NATO war against Yugoslavia in 1999, the consulate was the focus of a series of peace demonstrations while at its previous address on Nikis Street – from where it was moved due to security concerns.