"We expect the service to take place on Monday at 7:00 pm [1700 GMT] in the cathedral," the spokesman said.
Seventy-eight people have been confirmed dead in the worst railway accident to hit Spain since 1944.
Of the dead, 75 have now been identified.
Two days after the crash a further 81 people remained in hospital with 31 in a serious condition.
Local government officials confirmed on Friday that they were trying to organise funerals for the victims but that their "priority remains attending to the injured, supporting the families and identifying the victims".
The cause of the disaster is still unknown, but it is suspected that the train was going at over twice the speed limit when it came off the tracks and slammed into a concrete wall.
The train driver, Francisco Jose Garzon Amo, has been detained by police on suspicion of criminal recklessness.