A gauge that indicated overheated air was entering a Spanair jetliner just under the cockpit forced pilots to scuttle a first attempt at takeoff, about an hour before the plane crashed in flames.

But airline officials refused to speculate Thursday on what caused the crash that killed 153 people, and aviation experts said the gauge was probably not a factor.

As investigators tried to reconstruct the last, hellish minutes of the MD-82's flight, relatives crushed by grief went to a makeshift morgue to identify loved ones. Officials said many of the bodies were burned beyond recognition.

Many of the victims in Wednesday's flight were families traveling to the Canary Islands, a Spanish beach resort off Africa's West Coast. Compounding the tragedy was news that at least 22 of those on board were children, including two infants. Only three youngsters were believed to be among the 19 survivors.

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Development Minister Magdalena Alvarez said 39 bodies have been identified, and that the process could take several days because forensic teams were using DNA to help make identifications.

Some mourners spent the night at the morgue, set up at Madrid's main convention center — the same facility used for bodies after the March 11, 2004 Islamic terror attacks that killed 191 people on Madrid commuter trains.

Amid the horror were several stories of hope, and others of sheer luck.

The three children who survived — boys aged 6 and 8, and an 11-year-old girl — all suffered relatively minor injuries. The older boy had nothing more than a broken leg, extraordinary considering the devastation at the crash site.

And then there was the Spanish couple who were three minutes late and missed the flight altogether. Ertoma Bolanos said he and his girlfriend Almudena checked in but did not make it to the gate in time. They learned of the crash when Magdalena's family called to say they had seen footage of it on TV.

"Today is another birthday," Bolanos said.

One day after the crash, Spanair gave new information about the plane's initial attempt to take off. Spokesman Javier Mendoza said an air intake gauge under the cockpit had detected overheating while the jetliner was taxiing, causing the plane to turn back. Technicians corrected the problem by essentially turning the gauge off.

Mendoza said the device is not on a checklist of equipment that has to be functional for a plane to depart, and that turning off such a device is an accepted procedure. The plane was eventually cleared by technicians, but crashed on its second attempt to take off, burning and breaking into pieces.

The company said it did not know if the gauge problem had anything to do with the accident, but two aviation experts interviewed by The Associated Press said it was not likely that such a seemingly minor problem could bring down a modern plane.

Alvaro Gammicchia, a pilot for the Spanish airline Iberia who has flown MD-82s for seven years, said that even without the gauge "the plane would not fail to the point of causing a tragedy."

The MD-80 series aircraft have a number of static ports or pitot tubes — tiny holes — near the nose of the aircraft, with different functions. They provide data on air speed, air pressure, and outside temperature to the cockpit instruments. If the pitot tube or the static ports were somehow physically blocked, cockpit instruments such as the airspeed indicator and the climb indicator would be unable to function, since they would not be receiving outside data.

In contrast, probes for the engine instruments are located around the engines themselves.

Patrick Smith, a U.S.-based MD-80 pilot and aviation author, said by telephone that the gauge — also known as a probe — was not likely to have been involved.

"Most likely, whatever the malfunction of the probe was, it is probably not related to what happened," he said by telephone.

As investigators headed for the crash scene — including a team from the U.S. National Transportation Safety Board and representatives of airplane manufacturer Boeing — attention was also focusing on the plane's two black box recorders, which might provide further clues into the accident. Mendoza, the Spanair spokesman, said both had been recovered, and one had been damaged.

The Spanish newspaper El Pais reported that one of the two engines failed and may have caught fire during takeoff. La Vanguardia said witnesses saw the plane's left engine explode and catch fire before the aircraft went down.

The government on Thursday released a list of the nationalities of 19 foreigners from at least 11 countries who were on the plane. Of the 19, only one survived, a Swedish citizen. 1/4

The other 10 countries are: Germany with 5 citizens among the dead, France with 2, and one each from Mauritania, Turkey, Brazil, Indonesia, Bulgaria, Italy, Colombia and Gambia. The nationalities of three other foreign victims had yet to determined. The list did not name the foreigners.

As the shock of the tragedy began to sink in, Spain began three days of mourning Thursday. Flags in Madrid flew at half-staff and silent vigils were held at noon around the country. The king and queen visited the morgue, consoling relatives of those who died.