An estimated 10,000 people gathered in Lommel, a town in northern Belgium, to attend a memorial service for the victims of last week's bus crash in a Swiss tunnel.

A total of 52 schoolchildren and their chaperones from two Belgian schools were returning from a trip in Switzerland -- a week-long vacation of ski lessons, surprise parties, and barbeques -- when their bus crashed in a tunnel killing 28 (including 22 children) and injuring 24.

Most of the victims were Belgian or Dutch nationals

The cause of the crash is still under investigation.

In the Lommel memorial, soldiers carried the coffins of 14 children -- all of whom were 11 and 12 years old -- and their teacher from the Stekske School, into the large community center during a tearful procession attended by the victims' families and thousands of other Belgians mourning the tragic loss.

Belgium's King Albert II, and Belgian Prime Minister Elio Di Rupo also attended the service and were joined by Dutch Crown Prince Willem Alexander, and Dutch Prime Minister Mark Rutte, as six of the chidren were Dutch nationals. The ceremony was projected on two giant screens for the thousands gathered outside the halls to watch.

During the three-hour ceremony, family members of the victims shared stories and classmates sang songs to commemorate and mourn those who had been lost. One of the mothers remembered how her daughter, loved going to school and enjoyed all the teachers. Others spoke of the joy these children brought to their lives and of how difficult it will be to cope with the tragedy.

Peter Vanvelthoven, the mayor of Lommel, also shared his thoughts during the ceremony and wondered: Is there something worse than parents who lose what they love most?

Private burials followed the ceremony -- most of the children and their teacher were buried side by side. Another memorial will be held on Thursday in the town of Heverlee for victims from the second school.