Officials said on Monday the coroners were attempting to determine whether the people on board the Helios Airways flight were already dead when the plane slammed into a mountain just north of Athens early on 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."
The authorities also said the plane's two black-box recorders were being sent to France for expert examination.
They added that 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.
Investigators also were trying to determine why the pilot was not 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.
According to a list of the dead released by the Cypriot government, there were 20 children aged under 16 on board Helios Airways flight ZU522 from Cyprus to Athens. The youngest was four.