The underwater probe being used to look for missing Malaysia Airlines Flight 370 was back in the water after its first attempt ended prematurely, said the company that owns the vehicle, Phoenix International.
The Bluefin-21 autonomous underwater vehicle was about four hours into its second dive mission at 2 p.m. ET on Tuesday (2 a.m. Wednesday in Perth, Australia), a source close to the operation told CNN's Brian Todd.
On Monday, crews sent the probe toward the ocean floor on what was expected to be a 20-hour deployment, only to have it return in less than eight hours after encountering waters beyond its 4,500-meter (14,764-foot) maximum depth.
The probe found no debris during its shortened scanning session.
The second mission is expected to end Wednesday around 10 a.m. ET (10 p.m. in Perth), the source said. The vehicle was deployed in nearly the same area and is operating at about the same depth as the earlier mission, the source said.
The earlier aborted mission doesn't mean anything is wrong with the probe, which is designed to swim about 30 meters (100 feet) above the ocean floor and use sound waves to draw a three-dimensional map of what lies below.