US investigators have recovered a large piece of one of the space shuttle Columbia's wings which could provide important clues to the cause of the disaster. Investigators are working to establish which wing the piece belonged to. Nasa appeared to play down a fresh piece of photographic evidence which reportedly shows serious structural damage to the shuttle's left wing Mourning for the seven-strong crew of Columbia, which disintegrated as it returned to Earth last Saturday, has continued with a service at Kennedy Space Center in Cape Canaveral, Florida. http://news.bbc.co.uk/1/hi/world/americas/2739347.stm