LONDON – An investigation into the May 9 crash of an Airbus A400M airlifter is focusing on the aircraft’s TP400 engines and associated fuel system.

Four crewmembers — two test pilots and two flight-test engineers — died when the aircraft went down in fields north of San Pablo airport in Seville, Spain.

Two other engineers were pulled from the wreckage alive by farmers working on nearby land. They are both reported to be hospitalized in serious condition.

The A400M-MSN23 — destined for the Turkish air force — was undertaking its first flight from the airport, home of Airbus Defense & Space’s A400M production site and test facilities. As the aircraft took off from Runway 09, the crew immediately reported technical problems, which a German news outlet has described as multiple engine failures. The crew attempted to return to the airport’s Runway 27, but the A400M struck electricity pylons before making a hard landing on agricultural land near an airport industrial estate.

The engines — developed by the Europrop International consortium — are among the most complex elements of the aircraft. The powerful turboprop produces 11,000 shp and is the most powerful engine of its kind produced in the West. But it has had its fair share of development issues and was partly responsible for delays in the A400M’s first flight.

Both the flight data recorder and the cockpit voice recorder were recovered from the aircraft’s wreckage on May 10 and are now being examined by a joint team from the Spanish ministries of development and defense.

The aircraft had been due for delivery to the Turkish air force next month.

The U.K. defense ministry has halted operations with its two A400Ms until more information emerges about the accident’s cause. Germany and Malaysia also have halted flights.

The French defense ministry on May 11 declined to comment on the crash or its impact on the French A400M fleet.

“There will be no press release. We stick with what has been said by the defense minister,” a French air force spokesman said May 11.

The spokesman was referring to Jean-Yves Le Drian’s May 10 statement saying France would continue with “priority flights” of its six aircraft until the investigation uncovers the root cause of the incident.

“All our A400Ms are currently in operation,” he said, adding that the French fleet has accumulated 1,700 flights hours to date. “It is a high-quality, very efficient aircraft. We’ll support Airbus in order to discover what happened, what are the responsibilities, in all transparency.”

Airbus Defense and Space has so far delivered 12 A400Ms to four nations: six to France, two to the U.K., two to Turkey and one aircraft each to Germany and Malaysia.

The company plans to resume test flights May 12.