Experts are carring out tests on the remains of the passengers and crew of the crashed Cypriot airliner to determine when the 121 people died, while the plane's two black-box recorders have been sent to France for examination.
The coroners were attempting to determine whether the people on board the Helios Airways flight were already dead or still alive when the plane slammed into a mountain just north of Athens early Sunday afternoon.
"We will seek to determine when they died and how they died," chief Athens coroner Fillipos Koutsaftis said. "It will be an attempt to determine the causes."
Authorities said the cause of Sunday's crash appeared to be technical failure - resulting in high-altitude decompression. A transport official had said the 115 passengers and six crew may have been dead before the plane crashed.
"We will carry out a toxicological examination to find out if the victims died before or during the crash," he said.
Koutsaftis said a team of coroners also would examine blood and tissue samples from victims' lungs to determine whether anything the passengers and crew breathed in could have caused their deaths.
Searchers were still looking for three bodies, firefighting officials said. The three reportedly included the plane's German pilot, who was identified by Cypriot authorities as Marten Hans Jurgen, 50, from Berlin.
A spokesman for the German Foreign Ministry, speaking on condition of anonymity in line with German practice, identified one of the pilots as a 58-year-old German. It was unclear why there was a discrepancy in the age. Greek and Cypriot authorities often list surnames before given names, and Hans-Juergen would likely be the pilot's first name.
Investigators also were trying to determine why the pilot appeared to have not been in his seat when two Greek air force fighter jets intercepted the plane after it lost contact with air traffic control over the Aegean Sea.
Greek Deputy Health Minister Giorgos Constantopoulos said there had been 21 children on board Helios Airways flight ZU522 from Cyprus to Athens, "all aged 4 and above." Greek and Cypriot officials had originally said there were 48 children on the plane. No explanation for the discrepancy was given.
According to a list of the dead released by the Cypriot government, at least 10 families with children were among the dead. The passengers and crew included at least 12 Greeks and the German pilot, and a four-member family of Armenian origin. The rest were Cypriot.
The body of the Cypriot co-pilot, Pambos Haralambous, reportedly was found in the cockpit. The pilots of the Greek F-16 fighter jets had reported seeing him slumped over the controls of the Boeing 737 as it flew toward Athens from Larnaca, Cyprus.
Greek state television had quoted Cyprus' transport minister as saying the plane had decompression problems in the past. But a Helios representative said the plane had "no problems and was serviced just last week."
The plane, which had been scheduled to continue to Prague, Czech Republic, after Athens, crashed at 12:05 p.m. (0905 GMT) Sunday near Grammatiko, a village 25 miles (40 kilometers) north of the Greek capital.
Relatives of the dead gathered at a central Athens morgue to identify the victims.
In Cyprus, Helios Airways Chairman Andreas Drakos said the airline's crews were operating normally Monday, rejecting earlier reports that its pilots and crew were refusing to fly. Athens International Airport's flight information service listed a Helios Airways flight from Prague as landing Monday as scheduled.
The head of the Greek airline safety committee, Akrivos Tsolakis, said the two recovered black boxes - a data and cockpit voice recorder - were being sent to the French air safety investigators in Paris for further examination.
The voice recorder, Tsolakis said, was badly damaged by the crash and ensuing fire.
"It's in a bad state and, possibly, it won't give us the information we need," he said. "Both boxes will be sent to Paris where a French committee will help us and the foreign experts that are here to decode"
He said he believed his committee would be able to reach a conclusion "in a few days, a very few days."
Tsolakis said Greek investigators were to be joined by U.S. experts following a request by the American government because the aircraft was manufactured in the United States.
The airliner's pilots had reported air conditioning system problems to Cyprus air traffic control about a half-hour after takeoff. Shortly after entering Greek air space over the Aegean, the Boeing 737 lost all radio contact.
When the F-16s intercepted the plane at 10,400 meters (34,000 feet), jet pilots said they could not see the captain in the cockpit, and reported oxygen masks dangling inside the cabin, Greek government spokesman Theodoros Roussopoulos said.
He said the fighter jet pilots also saw two people possibly trying to take control of the plane; it was unclear if they were crew members or passengers.
Above 9,000 meters (30,000 feet), the effects of depressurization are swift, said David Kaminski Morrow, of the British-based Air Transport Intelligence magazine.
"If the aircraft is at 30,000 feet (9,000 meters), you don't stay conscious for long, maybe 15 to 30 seconds," he said.
Cyprus declared three days of national mourning, and in Athens flags were ordered to fly at half- staff on Tuesday. A 40-day mourning period was declared in Paralymni, a Cypriot town of 10,000 that lost 16 residents on the plane, the AP reported.