Australia decided Monday to deploy a mini-submarine to scour the unmapped Indian Ocean seabed for Malaysian jet MH370 at a daunting depth of 4,500 meters (15,000 feet), ending the search for black-box signals.
Angus Houston, who heads the Joint Agency Coordination Center, also revealed that an oil slick had been sighted in the area of the search led by the Australian vessel Ocean Shield far off Perth.
"Ocean Shield will cease searching with the towed pinger locator later today and deploy the autonomous underwater vehicle Bluefin-21 as soon as possible," Houston said, adding it could enter the water later Monday.
"We haven't had a single detection in six days so I guess it's time to go underwater," he told a news conference. "We anticipate deploying it this evening."
The US Navy said the vehicle would deploy at 5:00 pm Perth local time (0900 GMT), but did not immediately confirm the launch after the specified time.
"(It) will descend to a depth of between 4,000 and 4,500 meters, approximately 35 meters above the ocean floor," the navy said in a statement. "The AUV will spend up to 16 hours at this depth collecting data, before potentially moving to other likely search areas," it added.
Malaysia Airlines Flight MH370 went missing on March 8 en route from Kuala Lumpur to Beijing with 239 people on board. The reason why the plane came to crash in the southern Indian Ocean remains a mystery.
So far no debris has been found despite an enormous search involving ships and planes from several nations. But Houston said about two liters of the newly spotted oil slick had been collected for testing.
"I stress the source of the oil is yet to be determined but the oil slick is approximately 5,500 meters downwind... from the vicinity of the detections picked up by the towed pinger locator on Ocean Shield," he said.
It would be a number of days before the oil could be conclusively tested ashore, but Houston said he did not think it was from one of the many ships involved in the search.
"It's very close to where the transmissions are coming from and we'll investigate it and that will take a little bit of time, given that we're in the middle of the Indian Ocean.
Slow and Painstaking
Houston emphasized that it was 38 days since the Boeing 777 vanished and the batteries powering the black box tracker beacons had a life of only 30 days.