Olivier Elsig, prosecutor for the Valais canton (pictured), met with parents of victims last week in Sint-Truiden and reported that the investigation had ruled out three possible causes: the driver was not going too fast, there was nothing technically wrong with the bus, and there was no other vehicle involved in the accident.

Regarding exactly what did cause the bus to crash, Elsig had no firm news to report. The origin of the crash, he told a press conference in Brussels after the meeting, most likely lies with simple human error.

Swiss investigators are looking again at video images from the tunnel and at the medical records of the two chauffeurs to determine if driver Geert Michiels, 34, may have become unwell and lost control of the bus. A toxicological investigation is still under way, but alcohol has already been ruled out.

The accident happened when the coach grazed the right-hand wall of the tunnel, then about 75 metres on collided head-on with the corner of a safety niche. The bus was travelling at about 100 km/h, exactly the speed limit in the tunnel.

The full investigation is expected to take another three months, Elsig said, at which point the Swiss authorities will give a press conference to announce their findings.

“My husband was a very responsible driver with a lot of love for his job,” commented Michiels’ wife Evy Laermans. She was not aware of any health problems. The Swiss prosecutor’s report was welcome in providing more information, she said, although she was disappointed that Swiss authorities had ruled out the coach’s cruise control as a possible cause of the accident. The equipment was destroyed in the crash.