MADRID - SOME of the 154 people who died in last week's Spanair jet crash may never be identified, the government said on Monday, as investigators reportedly looked into whether a sudden loss of engine power caused the accident.

'Will anybody remain unidentified? I can't say at this moment but the possibility exists,' Interior Minister Alfredo Perez Rubalcaba told radio Cadena Ser.

Seriously damaged remains and difficulties in getting DNA samples from direct relatives of some victims were complicating the task, he said.

Forensic experts have so far identified the bodies of 96 victims, national radio said late on Monday.

The death toll rose to 154 on Saturday after a 31-year-old female lawyer died in a hospital after initially surviving the crash, despite suffering burns on 72 per cent of her body.

But in a piece of good news, a six-year-old boy who suffered head injuries and cuts on his face on Monday became the first survivor to be released from hospital, the Madrid health service said in a statement.

It said the 17 others remain hospitalised, two of them in 'very serious' condition, including a 44-year-old woman who had entered a coma from which there was no expectation of recovery.

The condition of the only other child who survived the crash, an eight-year-old boy, was improving, the health service said.

The MD-82 twin-engine jet crashed and burst into flames moments after taking off on Wednesday from Madrid's airport for Spain's Canary Islands.

Investigators are analysing whether a sudden loss of engine power could be to blame for Spain's deadliest air crash in 25 years, top-selling daily newspaper El Pais reported, citing unnamed police sources close to the probe.

Officials are following this line of investigation because an airport video recording of the ill-fated take-off shows the plane lifted itself off the ground about 500 metres later than it should have, it said.

Investigators think the plane's reverse system - which is used to help it slow down during landing - may have been automatically activated for unknown reasons in the right-sided engine, the newspaper said.

This could explain why the single-aisle plane tilted to the right immediately after take-off before crashing, it added.

The head of Spain's civil aviation authority AENA, Mr Manuel Bautista, refused to comment on the possible causes of the accident at a news conference on Monday, saying only 'there were probably errors and probably more than one.'

Some Spanish newspapers have tried to link the crash to Spanair's financial problems and cost-cutting measures, but Bautista said the carrier had passed over 100 inspections so far this year.

'In all the inspections we have not detected any problem that affects security or a link with cost-cutting policies,' he said.

Spanair, Spain's second largest airline, announced in July it would shed 1,100 of its 4,000 employees and cut its 65-plane fleet by 15 in September as part of a restructuring plan.

Daily newspaper El Mundo cited an unnamed former Spanair pilot on Friday who said 'the airline put pressure on mechanics for them to authorise planes to take off even if they (were) not ready.'

Just hours before the crash the national pilots' union Sepla had accused the carrier, which is owned by Scandinavian airline SAS, of 'organisational chaos' and 'serious deficiencies' in its operations.

But in a statement issued on Monday, the union, which also represents about 90 percent of Spanair pilots, said the carrier's 'flights and planes are absolutely safe and respect all operational security standards.'

'At Spanair, no pilot faces pressure to fly a plane that does not meet all the standards of operational security,' it added.

The Spanish government has vowed a full investigation into the causes of the accident. The head of the investigation team, Emilio Valerio, has said that the results of the probe would be known in about a month. -- AFP