ABOARD PATROL SHIP HAIXUN 01, April 8 -- Four Chinese and British vessels are trying to pick up the suspicious pulse signals detected by Chinese patrol ship Haixun 01 in an expanded search area on Tuesday.

Haixun 01, searching for missing Malaysian passenger jet MH370, detected on Friday a pulse signal with a frequency of 37.5 kHz -- the same as those emitted by flight recorders, and re-detected on Saturday the pings for 90 seconds just two km away from the original spot.

Haixun 01, Donghaijiu 101 and navy vessel 999 of China, as well as British HMS Echo, are scanning an expanded area of 432 square km at around 25 degrees south latitude and 101 degrees east longitude in southern Indian Ocean waters where the pulse signals were first detected.

Jiang Long, captain of Haixun 01, said the ship was deployed to the western part of the search area, Donghaijiu 101 to the most possible central part, and navy vessel 999 to the east, under the coordination of China Maritime Search and Rescue Center.

An Australian ship equipped with U.S. towed pinger on Monday detected two more acoustic events consistent with those emitted from aircraft black boxes within the northern part of the defined search area.

Angus Houston, heading the Joint Agency Coordination Center (JACC) which oversees the international search for the missing flight, described the detection as "the most promising lead" and "the best information" so far in the search effort.