Up to 60 people have been killed and around 125 injured after a train derailed outside the city of Santiago de Compostela in the region of Galicia in northwestern Spain on Wednesday evening.
This is only a provisional number and could rise further, a government spokeswoman said on Thursday.
As to the cause of the derailment, she said it appeared to have been due to an accident.
Families of the victims have arrived at the scene of the accident, waiting silently for further information.
Theresia Marin, a psychologist from eastern Spain, said she passed by the site at evening when the derailment happened. After hearing about the accident, she initiated to offer psychological help for the injured and victims' families at a temporary settlement.
Rescue operation has been well underway at the site, she said.
The earlier number of victims was under 50.
"The priority is to help the injured at the moment, sadly many of them are in delicate state and to help their families. We are working with enormous logistical capacity, but we cannot sadly save the lives of those 45-47 people, which is the number of deaths we are currently working with," said the President of the Galician regional government Alberto Nunez Feijoo on Spanish television after hours of the accident.
The train, which was travelling from Madrid to Ferrol and left the Chamartin Station in the capital at 15:00, derailed on a bend shortly after coming out of a tunnel.
At least 13 carriages came off the rails with several lying on the side of an embankment with several of them catching fire. Reports said that several of the carriages literally flew through the air.
Huge numbers of emergency services are at the scene in order to help the injured, along with a crane to help free those trapped in the wreckage.
Both of the train's drivers have survived the accident and will be able to help resolve the cause of the disaster, but for the moment the cause of the crash is not yet known.
Early indications are that it could be the result of human error, while some survivors have said the train appeared to be travelling at an excessively high speed on a curve with a speed limit of just 80 kilometers an hour.
Investigators have indicated the train could have been travelling at 180 km/h at the moment when it came off the rails and one of the drivers was reported to have confirmed the train took the curve prior to the accident at a speed of 200km per hour.
The bend where the accident happened is reported to be the tightest between the cities of Ourense and Santiago and was described as a "difficult section," of the track by the ADIF, the company which administers the infrastructure of Spain's railways.
There are also unconfirmed reports of an explosion on board, just as the train entered the curve, although the Spanish minister of the interior has ruled out a terrorist attack.
There were 218 passengers plus crew aboard the train, which was especially full because Thursday is the holiday of St John in Santiago, the patron saint of the region of Galicia and the start of a four-day weekend in the region.
The local authority in Santiago has announced that it has cancelled the celebrations which were due to be held over the coming days as a result of the tragedy to show respects to the victims.
The first event to be cancelled is the traditional firework display due to be held in the Plaza del Obradoiro in Santiago on Wednesday night.
Meanwhile the University Hospital at Santiago appealed for blood donors to help the victims of the crash and such was the response that all centers in the city were saturated with donors by 23:30 local time, although the police informed those wishing to make a donation could do so in hospitals in the nearby cities of La Coruna and Vigo.
The mayor of Santiago Angel Curras and Feijoo arrived at the site around 22:00 local time, while Spanish Prime Minister Mariano Rajoy, who is from Galicia, will travel to the accident site on Thursday morning.
Meanwhile King Juan Carlos of Spain has phoned Feijoo to express his condolences, while opposition leader Alfredo Perez Rubalcaba spoke of his 'consternation' at the disaster.
It is the worst train accident Spain has suffered in the past 40 years and the third worst in the country's history, with a higher number of victims than the head-on collision in Chincilla (Albacete), which claimed 19 lives in 2003.
The country's worst ever rail accident happened in January of 1944 on a train between Madrid and La Coruna with estimates of victims ranging from the official figure of 78 to over 500 dead.