Investigators are examining the fuel of a Tunisian twin-engine plane that crash-landed into the sea off Sicily killing 13 on board.
Some of the wreckage has been recovered from the sea
Both the quality of the fuel and the possibility that the fuel gauge was not working properly are being checked.
The Tuninter ATR-72 turbo-prop plane had 39 passengers and crew, 23 of whom were rescued. Three are still missing.
The plane was on its way from the southern Italian town of Bari to the Tunisian island of Djerba on Saturday.
Vito Riggio, the head of Italy's civil aviation body ENAC, told the Associated Press that the aircraft could have run out of fuel.
He said the plane had taken on very little fuel in Bari, where it had stopped for 20 minutes. Mr Riggio said the fuel cistern used to refill the plane in Bari had been tested and "the result was good".
Italian investigators have asked the Tunisian authorities to test the fuel loaded on in Tunisia.
AP reports that autopsies carried out on the 13 dead showed that most had died on impact, rather than from drowning.
"We were able to conclude that some of the passengers died while still wearing their seat belts," said Paolo Procacciati, head of the forensic medicine department at Palermo Giaccone Polyclinic.
Some survivors have told how they heard first one, then the other of the aircraft's two engines go silent just before the plane hit the water.
Most of the passengers were young Italian tourists, while the crew of Flight TUI 1153 was said to be Tunisian.
The French-made ATR-72 plane can carry up to 72 passengers.
The search for the three missing - two passengers and a mechanic - was continuing 20 miles (30km) in every direction from the crash site, off the Sicilian coast, on Monday.
Port Commander Vincenzo Pace told reporters on Monday that the decision to call off the search for survivors would lie with him.
"The decision, painful as it will be, to call off the search will be made by me after considering... factors including [water] temperature, human resistance and weather," he said. "We don't want to feed false hopes."
Some of the wreckage has been brought ashore, but it is unclear whether the authorities will try to recover the black box flight data recorder from the seabed.