PERTH, April 17-- Preliminary analysis of the sample from the oil slick collected by Ocean Shield has confirmed that it is not aircraft engine oil or hydraulic fluid, the Joint Agency Coordination Center (JACC) confirmed in its latest update later Thursday.

At the media conference on Monday, Chief Coordinator of JACC and Retired Air Chief Marshal Angus Houston said that the Australian Defence Vessel Ocean Shield had detected an oil slick Sunday evening in the current search area.

The JACC confirmed earlier Thursday the oil sample collected by Ocean Shield had arrived in Perth and would be subject to detailed testing and analysis.

In addition, Phoenix International, with the assistance of Bluefin, have assessed that there is a small but acceptable level of risk in operating the vehicle in depths in excess of 4,500 meters.

"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.

The JACC also stressed that some media reports on Thursday said that it would take Bluefin-21 anywhere from six weeks to two months to scan the entire underwater search area. "This is incorrect," the JACC emphasized. "Since the U.S. Navy provided comments 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 Ocean Shield," its latest update showed.

And the JACC confirmed that this analysis had allowed the definition of a reduced and more focused underwater search area. "This represents the best lead we have in relation to missing flight MH370 and where the current underwater search efforts are being pursued to their completion so we can either confirm or discount the area as the final resting place of MH370," the JACC said.

Malaysian flight MH370 went missing on March 8. An international effort to search for the missing plane has been underway since then.