BEIJING, April 7 -- Four Chinese ships and a British ship Monday continued the hunt for the missing flight MH370 in an expanded area in the South Indian Ocean, where a Chinese vessel had earlier picked up a pulse signal consistent with flight recorders.

Meanwhile, an Australian ship has detected two more acoustic events possibly from airplane black boxes.

The five vessels are Haixun 01, which picked up the pulse signal on Friday, Donghaijiu 101, Chinese naval ships Jinggangshan and Kunlunshan, as well as the British HMS Echo.

The search began at 8 a.m. Beijing time in a sea area of about 144 square km, which is around the point (25 degrees south latitude and 101 degrees east longitude) where the pulse signal was detected last week.

The four Chinese vessels were scheduled to search in the western part of the area until 2 p.m. on Monday, when they would switch with the British HMS Echo to the eastern part.

On Friday, Haixun 01 detected a pulse signal with a frequency of 37.5 kHz -- the same as those emitted by flight recorders -- in this search area, and redetected the pings for 90 seconds on Saturday just two km away from the original spot.

However, neither of the signals has been confirmed as related to the missing Malaysia Airlines jetliner, the China Maritime Search and Rescue Center said.

Also on Monday, an Australian official said an Australian ship detected two more acoustic events possibly from airplane black boxes in the past 24 hours in the South Indian Ocean.

"The towed pinger locator deployed from the Australian Defense Vessel Ocean Shield has detected signals consistent with those emitted from aircraft black boxes," said Angus Houston, who heads the Joint Agency Coordination Center (JACC) which oversees an international joint search mission for the missing flight.

The two separate signal detections occurred within the northern part of the defined search area and would be consistent with transmissions from both the flight data recorder and the cockpit voice recorder, said Houston, former Australian defense minister and a retired air chief marshal.

Describing the new detection as "the most promising lead" and "the best information" so far in the search effort, Houston warned it has to be treated cautiously and responsibly until final determination is made.

He said the first thing to do before these leads could be possibly verified is to fix the position of the signals, then Ocean Shield could deploy the autonomous underwater vehicle, Blue Fin 21, into the water and attempt to locate wreckage on the sea floor.

According to the JACC, up to nine military planes, three civil planes and 14 ships will assist in Monday's search for missing flight MH370 with a search area approximately 234,000 square km.

Malaysia's acting Transport Minister Hishammuddin Hussein said on Monday that he was cautiously hopeful that there could be positive developments in the search for flight MH370 "in the next few days if not hours."

When asked about the ownership and leadership of the investigation of the black box if it could be recovered, Hishammuddin said, "We will follow the ICAO practices, and we will inform developments in respect of investigations basing on whatever we find in due course."

However, he said what they focused on right now was to find the black box first.

Also on Monday, former Malaysian Prime Minister Mahathir Mohamad justified the efforts made by the Malaysian government in dealing with the incident, saying they were doing "everything possible."

In an interview with Xinhua, Mahathir said he believed the search would take a long time as so far there had been no clear indications where the plane was.

Regarding the joint international effort in the search operation, Mahathir said, "The fact that 26 countries are involved in the search is not just because of humanitarian reason, it is because they need to know what happened."

"Because if this can happen to the plane, it may happen to other planes. So they must know how it happened, so they can ensure that it will not happen again," he said.