Missing plane's black boxes may have gone silent

Search continues without help of the electronic pings from Malaysian flight

After four strong underwater signals in the past week, all has gone quiet in the hunt for missing Malaysia Airline Flight MH370, indicating that the batteries on the all-important black boxes may have finally died.

Crews continued searching on Sunday for debris and any potential pings in an effort to pinpoint where the Boeing 777 might be in an enormous patch of the southern Indian Ocean.