The search for the missing Malaysia Airlines flight is focused on two areas of the Indian Ocean where possible "black box" signals have been detected. The BBC's Nick Childs looks at how reports are being investigated. There are multiple cautions, caveats, and questions. But in a frustrating search that has produced very few clues, and still zero physical evidence of a possible crash location, the search teams have to take these reported acoustic contacts seriously as possible leads, not least because of the potential prize they could offer of dramatically narrowing the search area. Hence the redeployment of ships and aircraft to pursue them. The reported contacts…