KUALA LUMPUR, Malaysia — With no trace of Malaysia Airlines Flight 370 more than three weeks after it disappeared, the international search effort intensified early Monday, with 10 planes and 10 ships expected to scour the latest search area, officials said.
Other ships were en route to the zone, about 1,100 miles west of Perth, Australia, and were expected to arrive in the next several days. They include an Australian naval vessel, the Ocean Shield, outfitted with special equipment to detect the pings of the plane’s data recorders, or black boxes, according to the Australian Maritime Safety Authority, which is coordinating the search.
As in the two previous days of searching, aircraft spotted more debris floating in the zone’s rough waters Sunday, the authority said.
At least four orange objects that were more than 6 feet long were seen by the crew of an Australian P3 Orion search plane, the pilot, Flight Lieutenant Russell Adams, said after returning to base, the Associated Press reported.
Adams noted that the origin of the objects had not been determined, but he said it was ‘‘the most visibility we had of any objects in the water and gave us the most promising leads.’’
A day earlier, crews on two of the ships pulled several objects from the zone’s rough waters, raising hopes that perhaps the first physical evidence of the missing Boeing 777-200 had been found.
But the debris turned out to be “fishing equipment and other flotsam,” the authority said in a statement late Sunday.
The planes taking part in Sunday’s search included three Australian P3 Orions, a Japanese P3, a Chinese Il-76, a Korean Orion, a US Poseidon, and two Malaysian C-130s.
Information on the flight data and cockpit voice recorders may help investigators resolve what happened on Flight 370. Possible theories include equipment failure, a botched hijacking, terrorism, or an act by one of the pilots.
In Malaysia, more than two dozen relatives of Chinese passengers on Flight 370 arrived from China on Sunday to press Malaysian officials for more answers about the investigation.
The Malaysian government has endured withering criticism from the relatives and friends of Chinese passengers, both in Malaysia and in China, who have accused officials of withholding information about the disappearance of the plane and not doing enough to find it.
The group protested at a hotel near Kuala Lumpur and demanded an apology from the Malaysian government for declaring last week that the plane had crashed into the Indian Ocean, saying there was insufficient evidence to support that conclusion.
Government officials said later that they planned to hold a briefing for the family members that would include “high-level representatives of the Malaysian government.”
The Ocean Shield, the Australian offshore support vessel that will be carrying the ping-detecting devices, was supposed to leave Perth on Sunday, but its departure was rescheduled for Monday, officials said. The ship will also be carrying an unmanned underwater vehicle.
The frigate HMAS Toowoomba left Perth on Sunday and should arrive at the search area in about three days.
The value of the ping detector, in the absence of more specific information about the location of the wreckage, is questionable.
The device will be towed behind the ship at no more than about 6 miles per hour and has to be within about a mile of the black boxes to pick up the signal reliably, making for a slow and painstaking process. The new search area, which was established Friday, is roughly the size of Poland.
Searchers, however, say there is no time to waste: The device will be ineffective once the batteries powering the black boxes die, which is expected to happen next week.
The recovery of debris from Flight 370 might not necessarily pinpoint the location of the wreckage. When debris is found quickly enough after a crash into the sea, investigators can trace its drift back to the impact site and conduct an underwater search for the black boxes. But in the case of Flight 370, any debris, if found, might well have drifted hundreds of miles since the plane’s disappearance and be of limited use in finding the crash site.
The search area was shifted after new analysis of radar data from the morning of March 8 — when Flight 370 apparently veered off its intended route from Kuala Lumpur to Beijing — determined that the plane was traveling faster than previously thought and therefore would have burned fuel more quickly and possibly fallen into the Indian Ocean farther north than previously believed.