BRUSSELS, June 23 (Reuters) - NATO said on Thursday one of its websites was the subject of a probable data breach, but it did not contain any classified data.A NATO statement said access to NATO's public e-Bookshop, which is operated by an external company, had now been blocked.Police dealing with cyber crimes had notified the alliance of "a probable data breach", the statement said without providing details."NATO'S e-Bookshop is a separate service for the public for the release of NATO information and does not contain any classified data," the statement said.