PENGHU, Taiwan — Minesweeping ships helped investigators search Monday for the voice and flight data recorders from a China Airlines plane that broke apart high over the Taiwan Strait and crashed, killing all 225 people on board.
Officials initially believed they picked up the beacon signal of the "black box" about 23 miles north of the Penghu island chain off Taiwan's western coast.
But late Monday afternoon, Taiwan's Aviation Safety Council said the signal was not emitted by the black box.
One investigator, who spoke on condition of anonymity, told the Associated Press that low-frequency sounds made by ships and underwater objects often are mistaken for flight recorder signals.
The investigator also said strong winds and shifting tides have frustrated efforts to find the device.
This was the second time in two days that searchers mistakenly believed they found the black box's location.
Investigators said the black box might offer the best clues why Flight CI611 split into four pieces at 30,000 feet about 20 minutes after taking off from Taipei in clear weather for Hong Kong.
Taiwanese officials said there was no evidence of a terrorist attack, but they did not know what caused the catastrophe.
Investigators from the U.S. National Transportation Safety Board were due to arrive in Taiwan on Monday and fly to Penghu on Tuesday to assist in the probe because the crash involved an American-made Boeing 747-200. Boeing engineers arrived in Penghu on Monday.
Lee said the NTSB team was experienced in deep-sea diving and should be very helpful.
So far, only small pieces of the plane have been found and search teams were using sonar to find the large sections, said Andy Ju, an investigator working for China Airlines.
More than 80 bodies have been found and about half of them have been identified. Sobbing relatives collapsed into each other's arms as caskets were loaded onto planes Monday.
Investigators and officials declined to speculate on the cause of the crash, saying only that radar showed the plane broke into four pieces and that the pilots never reported a problem.
Taiwanese newspapers were filled with theories. Some said structural problems might have caused the 22-year-old plane to fall apart, others speculated that there was an explosion because radar showed one chunk of the jet shot backward while the other three parts went forward.
But Huang Lei, deputy director of the National Security Bureau, told reporters Monday there was no evidence of a terrorist attack or that a missile had downed the plane.
"None of the information we received proved any of the speculation," he said.
Taiwan's military has said it was not testing missiles or other weapons in the area.
The crash was a serious blow to China Airlines, which has been working hard in recent years to overcome a poor safety record.
The airline's stock plunged 7 percent Monday, the daily limit on Taiwan's market.
Also Monday, mainland China's state news agency issued scathing criticisms of the Taiwan government's response to the deadly crash.
The Xinhua News Agency report came just two days after the government offered condolences and assistance.
"Relatives of passengers expressed outrage over the slow pace of rescue work and some called on the Taiwan side to actively seek help from China," the report said.
One person quoted accused Taiwanese officials of merely "making a show" of joining in rescue efforts.