A British Navy survey ship arrived Sunday at the spot in the Indian Ocean where a Chinese vessel detected "pulse signals" Friday and Saturday that could be from the black box of the missing Malaysia Airlines jet, a Ministry of Defense spokesperson told NBC News.
The sophisticated HMS Echo is "capable of collecting an array of military hydrographic and oceanographic data," according to Britain's Ministry of Defense.
The Australian Navy's Ocean Shield, which is carrying high-tech sound detectors from the U.S. Navy, will also deploy to the location where the crew of Haixun 01 heard pulses, but not before investigating other sounds it picked up 300 nautical miles away from the Chinese ship.
Australian military aircraft were also sent into the Haixun 01's area to investigate, said Australian Air Chief Marshal Angus Houston, who is coordinating the search.
Searchers are racing against time to recover the battery-powered black box, which presumably holds data that could solve the mystery of why Flight 370 disappeared on March 8.
Black boxes emit pings so that they can be easily found — but the batteries drain in about a month.
The pulses detected by the Chinese ship are "an important and encouraging lead, but one which I urge you to treat carefully," Houston said Sunday.
While the pulses were consistent with the Boeing 777's black box, experts warned the way they were picked up by the Chinese ship and the length of detection — about a minute and a half — didn't make sense.
"The pinger itself is continuous, it’s not intermittent. Even if the battery was dying, it’s either working or it isn’t,” NTSB crash expert Greg Feith told NBC News Saturday.
The Australian and British ships drag detection equipment slowly behind the boats, which provides a more accurate read, The Associated Press reported.
— Elisha Fieldstadt and Peter Jeary, with The Associated Press