Over a month since Malaysia Airlines Flight MH370 went missing, the search continues for the Malaysian Boeing 777-200ER below the surface of the waters of the southern Indian Ocean.

After pings from Flight MH370’s black box went silent over the weekend, the focus of the search shifted to the sea floor. On Thursday, while air and ocean surface vehicles continued to scour their assigned search areas, the ADV Ocean Shield deployed the Bluefin-21 autonomous underwater vehicle (AUV) again, with the hopes that it may find any physical sign of Flight MH370 on sea floor of the southern Indian Ocean.

The Bluefin 21 was deployed multiple times earlier this week. However, its underwater missions were setback by some technical difficulties. Among some of the issues experienced, the Bluefin-21 was automatically forced to surface after it exceeded its maximum operational depth limit of 4,500 meters while traversing the ocean floor.

While the ocean floor may be too deep for official operational limits for the Bluefin 21, there’s hope that the AUV could be reprogrammed to operate at greater depths.

Phoenix International, the manufacturer behind the Bluefin-21 assessed that there’s a “small but acceptable” risk of operating the Bluefin-21 AUV below 4,500 meters according to an official statement from the Australian Joint Agency Coordination Center (JACC).

According to the JACC, the expansion of the Bluefin-21’s maximum operation depth will allow the AUV to scan the current search area within predicted limits.

The JACC refuted media reports which claimed the underwater search for Flight MH370 using the Bluefin-21 would take anywhere from six weeks to two months to scan the entire underwater search area. In addition, it also confirmed that an oil slick discovered by the vessel ADV Ocean Shield was not aircraft engine oil or hydraulic fluid.

While a definitive timeline of the underwater search for Flight MH370 was not given, the JACC emphasized that acoustic analysis of signal detections by the towed pinger locator on the ADV Ocean Shield has helped to narrow the search area for Flight MH370 significantly.

Malaysia Airlines Flight MH370 went missing along with its 227 passengers and 12 crewmembers on board in the early hours of March 8 during a flight from Kuala Lumpur bound for Beijing, China, triggering a massive search spanning the waters of Southeast Asia and the southern Indian Ocean.