Ambulances sit lined up to transfer recovered victims of the ill-fated Lion Air flight JT 610 as debris collected at sea sits out to dry, at the Jakarta International Container Terminal in Jakarta. BAY ISMOYO / AFP

Indonesian investigators searching for the flight recorders of crashed Lion Air flight 610 have heard transponder "pings" that could lead them to the devices, and answer questions as to why the new Boeing 737 MAX 8 went down, killing all 189 people on board.

Haryo Satmiko, deputy director of the National Transport Safety Committee, told CNN in a text message that, while the pings had been detected, investigators needed more "technical efforts" to find the exact location of the so-called black boxes.

Small pieces of debris and remains of some people on board the plane have been retrieved from the water off Jakarta, but the main body of the plane has been missing since it disappeared from radar on Monday around 6:30 a.m. local time.

Read more about the latest developments in the search for the crashed airliner here.