(ANSA) - Investigations into the crash of a Tunisian-operated passenger plane in the sea off Sicily on Saturday are focusing on possible problems in the fuel supply to the aircraft's engines.
The ATR-72 plane flying from Bari to the island of Djerba in Tunisia crashed after first one, then both its turboprop engines cut out. At least 13 of the 39 people aboard were killed.
Prosecutors in Bari, along with colleagues in Palermo, are considering at least three possible causes of the crash:
1) that the fuel was dirty or diluted;
2) that the system which injects fuel into the engines failed; or
3) that the plane ran out of fuel.
The plane, built by the French-Italian ATR consortium in 1992, was part of the fleet of Tuninter, the charter flight arm of Tunisian flag carrier Tunisair. Its wings, engines and part of the central fuselage have been salvaged. According to experts who examined the engines at the weekend, the chances of both engines breaking down are a million to one - unless the supply of kerosene dried up for some reason.
Prosecutors confirmed again on Monday that they had found "no trace of sabotage" and so they were concentrating their attention on the most likely alternative explanation. "We intend to run tests on the fuel and try to get results as quickly as possible," said Bari prosecutor Giuseppe Scelsi.
The plane reportedly took on board some 240 litres of kerosene in Bari, topping up fuel tanks which have a total capacity about 10 times that. The refueling unit from which the plane drew the kerosene has been impounded and samples taken for analysis.
But investigators noted that several other planes refueled from the same tank on Saturday and had no problems. Another possibility was that the mechanism which fed fuel into the engines broke down. But because the engines were fed independently, and both stopped within seven minutes of each other, this explanation also seemed unlikely.
A possibility seen as plausible by investigators is that there was a problem with the fuel gauges, which could have become blocked and showed 'Full' when tanks were half empty. This would explain why so little fuel was taken on board in Bari and why, after 90 minutes, the engines both cut out.
ENAC, Italy's civil aviation authority, has asked that tests also be carried out on the refueling units used by the ATR-72 in Tunisia before it flew to Bari on Saturday to pick up 34 passengers there.
Prosecutors have said they may also ask Tuninter, to contribute evidence to the investigation from documents at its disposal in Tunisia. The 13-year-old ATR-72, one of three in the Tuninter fleet, appeared to have no problems when checked over before take-off from Bari, airport officials said.
It underwent random checks by Italian airport officials four times, the last of which was on March 25 this year when it passed all 54 tests, national civil aviation agency ENAC reported.
Over the last year both of its engines were taken apart for routine checks by a specialist company based in Naples.
Italian Transport Minister has vowed that nothing will be left undone in efforts to find the cause of the crash and identify those responsible.
He also said on Sunday that Italian authorities would tighten up checks on aircraft used for charter flights in future.
