PERTH, Australia (AP) — Search crews today will send a sub deep into the Indian Ocean for the first time to try to determine whether signals detected by sound-locating equipment are from the missing Malaysian plane's black boxes.

The Bluefin 21 autonomous sub will be able to create a sonar map of the area to chart any debris on the seafloor.

Meanwhile, the head of the coordinated search says crews have not picked up a signal in six days.