Intelligence officials are still investigating all the clues they have to find out which group was behind the bombs.
Hundreds of people demonstrated noisily in Madrid earlier in the day. They claimed the government was trying to unfairly push the theory that the terrorist group Eta carried out the attacks.
Some of the clues have suggested al-Qaeda involvement, but others have pointed to Eta. It is thought the bombs were remotely controlled by mobile phone to explode.
All day, thousands of family, friends and loved ones have been remembering those who died in the blasts.
Children and adults have laid flowers, teddies and cards with sad messages on them around the city of Madrid and other cities on the second day of the country's official mourning.
More than 1,500 people were hurt in the 10 bombs which ripped through trains along Spain's busy train lines on Thursday morning.