Tearful and sorrowful Belgians observed one minute of silence on Friday to mourn the deaths of 22 children and six adults who died in a bus crash in the Swiss alps on Tuesday.

People gather for a remembrance service in Lommel, Belgium, in honor of the victims of the bus crash in Switzerland on Thursday. Twenty-eight people, including 22 children, were killed and 24 others were injured on Tuesday in the accident. The children, from two schools in Lommel and Heverlee, were on their way home after a ski vacation. Yorick Jansens / Agence France-Presse

With flags flying at half-mast in cloudy weather, the country came to a silent standstill at 11 am, after which, church bells reverberated in cities and towns across the nation.

At the Sint-Lambertus kindergarten and primary school in the tiny town of Heverlee, 20 minutes drive away from Brussels, nearly 200 children and teachers stood and joined hands in a playground to remember seven schoolmates, one teacher and one ski monitor from the school. After the memorial, together with school directors Marc Carels and Margriet Vanvolsem, they sent white balloons into the air to convey their sadness.

The other victims of the bus crash were from the Stekske primary school in Lommel, near the Dutch border. There, teachers and kids also participated in a moment of silence after a memorial service was held on Thursday in Lommel, according to AFP.

"These are tragic days for Belgium and my town," said Agnes Vandersypen, who lived just one block away from the school in Heverlee.

Vandersypen's granddaughter attends kindergarten at the Sint-Lambertus school. Just last week, her granddaughter and the children had held a memorial service for a car crash that occurred four years ago. In that crash, two students from the kindergarten and their mother died, leading the father to commit suicide afterward.

"And another tragedy happened and it is really too much and unacceptable for our small town," said Vandersypen, who put flowers at the gate of the three-story school.

Near the school gate and walls, drawings, greeting cards and small gifts have piled up. Local residents often gather to light candles and send flowers to express their sadness, love and condolences for the victims and their families.

One card reads: "Please don't feel too much sorrow and we will sing for you. With love."

According to the BBC, most of the victims of Tuesday night's disaster were around 12 years old. Although most of the children were Belgian, one British and six Dutch were among those killed. Six adults - teachers, drivers and ski monitors - also died.

By press time, two planes carrying the bodies of those killed had landed at Melsbroek military airport in Belgium after leaving Switzerland with a memorial ceremony. It was not known when the funerals will be held. "The government is still discussing with the parents," said the police spokeswoman in Heverlee.

According to the BBC, eight of the injured children were flown home on Thursday, but many survivors were still being treated at hospitals.

AP reported that trains and subways stopped in their tracks for the tribute, culminating three days of shock that slowly turned to heart-wrenching sorrow. Political leaders stood united in silence and Belgian churches slowly chimed their bells in unison.

The tourist bus carrying 52 people crashed head-on into a wall inside a tunnel as it headed home from a ski vacation in the Swiss Alps.

According to AP, Olivier Elsig, prosecutor for the Swiss canton of Valais, said the crash is being investigated for three possible causes - a technical problem with the bus, a health problem with the driver or human error.

Investigators have so far determined it was a modern bus with two rested drivers and said the tunnel was considered safe.

But the Switzerland Federal Office for Roads said on Friday it was examining whether the angle of the wall that the bus hit contributed to the severity of the crash. That part of the tunnel had a cutout for disabled vehicles, which meant part of the wall was at a right angle to the tunnel road.

"In principle there is the possibility of slanting the angle of the bay, or protecting it with concrete or other elements," spokesman Michael Mueller told AP.

The tunnel where the crash occurred opened in 1999 and the German automobile club ADAC gave it the second-best of six ranking levels in 2005.

"Such a severe and tragic accident must always be taken as an opportunity to analyze the factors that could have influenced the causes and effects of the disaster," Mueller told AP.

Agencies contributed to this story.

fujing@chinadaily.com.cn