Greece ? Carbon monoxide did not knock out some of the passengers and crew of a Cypriot airliner before it crashed in the Greek mountains, coroners said Friday, deepening the mystery as to what caused the disaster that killed all 121 people on board.

Fillipos Koutsaftis, chief coroner of Athens, said tests were carried out on the remains of the co-pilot, three female flight attendants, an infant and an adult who were on the flight that went down Sunday about 25 miles north of the Greek capital.

More tests were being conducted to determine what could have rendered crew and passengers aboard the Helios Airways Flight ZU522 from Larnaca, Cyprus, unconscious during the flight. The plane flew on autopilot before crashing.