from flight 370 in the coming days. >> there were four pings detected, making four since saturday. the analysis of of the first two signals indicated they came from an electronic device and are consistent with the ping of a flight data recorder. now the new development has the officials tightening the focus of the search. >> that is right, 15 aircraft and 14 ships are working a grid of about 75,000 square kilometers. >> but authorities say it is still too soon to deploy the u.s. navy's bluefin robotic search ve%!ñ they do want to define the search area with as many pings as possible before batteries in the plane's beacon die out. meanwhile, search leader angus houston is very cautious. listen. >> what we're picking up is a great lead. okay? we have to visually acquire before we can say this is the final resting place. so there is still a way to go.