At least 22 of the victims were children, most of them aged around 12. They were primary-school pupils from two small Flemish towns: Lommel, near the Dutch border, and Heverlee, east of Brussels.
Relatives have been gathering at the schools as authorities struggle to identify all those killed or injured. Parents are making their way to Switzerland today, where 24 children are still in hospital.
Meanwhile officials from all over Europe have been sending their condolences, with a minute's silence in the European Parliament in Strasbourg, France.