An oil slick found in the ocean where the search continues for missing flight MH370 was not from a plane engine or hydraulics, the search coordinators say.
In a statement released on Thursday night, the Joint Agency Coordination Centre (JACC) said preliminary analysis of a sample of the oil showed it was not related to the missing plane.
The JACC, headed by former Defence chief, retired Air Chief Marshal Angus Houston, said there is "a small but acceptable level of risk" in using the Bluefin-21 underwater drone to scan the Indian Ocean's seabed at depths below 4,500 metres.
"This expansion of the operating parameters allows the Bluefin-21 to search the sea floor within the predicted limits of the current search area," the JACC said.
JACC also rejected suggestions the drone could take between six weeks to two months to scan the entire search area.
"Since the US Navy provided comment some days ago, the underwater search has been significantly narrowed through detailed acoustic analysis conducted on the four signal detections made by the towed pinger locator on ADV Ocean Shield," the JACC said.
"This analysis has allowed the definition of a reduced and more focused underwater search area."