A five-minute silence has been observed across Spain in memory of the 41 people killed in Monday's underground train crash in the eastern city of Valencia.
The city of Valencia has declared three days of mourning
Families have been identifying bodies at the city morgue, and funerals attended by the royal family and prime minister are to be held in the evening.
Members of parliament in Madrid stepped outside to join the act of remembrance.
Investigators have found the train's black box which could yield more clues about the cause of the crash.
Two carriages left the rails and smashed into the walls of a tunnel near Jesus station.
At least 45 people were injured, and 12 were still in hospital soon after the crash. They include a pregnant woman and two people reported to be in a "very critical" condition.
Trade unions say it is too early to comment on suggestions that speeding or a collapsing wheel caused the crash.
Bereaved families filed through the morgue on Tuesday, many of them clearly in a state of shock.
Only one of the bodies reportedly remained unidentified.
The dead include the mother of an 11-year-old girl who is among the injured, Valencia's sub-prefect Luis Felipe Martinez was quoted as saying by AFP news agency.
A bouquet of red and white carnations and burning candles could be seen outside the Jesus station.
Traffic came to a halt and builders nearby paused for the silence at noon (1000 GMT).
"Spaniards' hearts are in Valencia," said Deputy Prime Minister Teresa Fernandez de la Vega afterwards.
King Juan Carlos and Queen Sofia are expected in Valencia, as is Prime Minister Jose Luis Rodriguez Zapatero, who cut short a visit to India following the crash.
Mr Martinez said on Tuesday that the cause of the crash was still an "open" question.
The previous day he said it had "apparently been brought about by excess speed and a failure at the wheel level".
A union spokesman, Jose Aroca, cautioned against "hasty speculation," saying it seemed "highly unlikely" excessive speed was to blame.
The train's driver is among the dead.
Spain's national police service has sent five specialist accident investigation officers from Madrid to Valencia to help establish why the train derailed.
With the 2004 Islamist bomb attacks on Madrid's rail network still fresh in Spanish minds, the authorities ruled out any terror link to Monday's crash.
The four-carriage train was travelling on Valencia's Number One underground route, close to a junction with another line. It came off the rails between Plaza de Espana and Jesus stations.
The train had passed a safety inspection just one week before the crash, Spain's Efe news agency reports.
Unions say the train line where the accident happened is the oldest in Valencia's metro network.
Last September, three underground trains collided in Valencia on the same line, injuring 29 people.
The accident comes days before Pope Benedict XVI is due to visit Valencia, with preparations being made for hundreds of thousands of pilgrims to use the city's public transport network.
The pontiff has prayed for the victims of the crash, the Vatican said.
Have you been affected by this incident?
I was at Jesus Metro Station only 25 minutes before the Crash today. I have been travelling on this line every day for the past 3 years. Line "1" is the oldest on the network and some of the trains are really in a poor condition. In some of the stations you can actually see water leaks gushing from under the tracks.
Nick Cheesman, Valencia, Spain
Fist of all I want to give my condolences to the people who have suffered in this catastrophe. I am very sorry. I have travelled on that line and every time I felt terrified. Trains stopped for technical failures, lights went off, etc. The trains were very old and should have been removed many years ago.
Carmen, Valencia (Spain)
I have lived in Valencia for 24 years. Yesterday I was broken when I heard the news. That underground line is the one of the busiest ones, since is leading to Universities from the outskirts of Valencia.
Jose Campins, Valencia
Many have complained in the past about the lack of improvements and decent maintenance of this line, very much used by students, workers, tourists... while the city builds opera houses and yacht clubs. The "authorities" blame the "speed".
Miguel García, Madrid, Spain.
I usually travel on that line and people have long been saying that it is in very bad condition. In the place where the accident happened there is a bend that makes the train shake tremendously. It was only a matter of time. All Valencia's citizens are dismayed.
José Miguel, Valencia, Spain
I would like to offer my most heartfelt feelings to the people families and all who were caught up in this. To me there seems to be an investigation needed into the the public transport and it's safety.
Simon Carney, Brighton UK
I still can't believe this has happened five minutes away from my home; it's the train station I use. I hope now they'll change old wagons and not only those which are in metro lines used by tourists.
Mireia Nicolas, Valencia - Spain