Police said the bus became engulfed in flames on a road in Kerzers, a town in the canton of Fribourg, about 20 km (12 ​miles) from the Swiss capital Bern.

“At this stage, we have elements suggesting a deliberate act by a ​person who was inside the bus,” Frederic Papaux, a spokesperson for Fribourg police, said.

Investigators were ⁠looking into reports that a person had poured fuel on themselves, said Christa Bielmann, another local police spokesperson.

​It was too early to say whether the incident was terror-related, she told a news conference.

“We have no indication ​that suggests we might be dealing with a terrorist attack,” Swiss politician Romain Collaud, a state councillor, told the Swiss-French broadcaster RTS on Wednesday morning, adding that investigations are ongoing.

Three injured people were taken to hospital, police said.

Two other people caught up in ​the blaze also received attention but did not need to be hospitalised.

On Tuesday evening passengers were seen escaping ​from the burning bus, panicked and injured, Papaux said, adding that no other vehicle was involved.

Swiss media outlet 20 Minutes said ‌it had ⁠seen a video taken at the scene in which an injured person said:

“A man set himself on fire. He poured gasoline over himself and then lit himself.”

Video after the flames were extinguished showed the charred remains of the vehicle, a yellow so-called Postauto.

The identification of the six people who died could take several days, Collaud said, adding ​it is not known if ​the person suspected of ⁠starting the fire was among the victims.

Swiss President Guy Parmelin offered his condolences and said the incident was being investigated.

“It shocks and saddens me that once again people ​have lost their lives in a serious fire in Switzerland,” he said in a ​statement on X, ⁠noting investigations were under way.

In January, Switzerland was rocked by a fire in a bar in the Swiss ski resort of Crans-Montana that killed 41 people and injured 115.

“The wounds from Crans-Montana are still fresh, fuelling strong reactions today,” Collaud ⁠said. “These are ​clearly events no one wants to experience, or relive.

Yet they ​seem part of everyday life now, happening more frequently in Switzerland and worldwide, which is unfortunate,“ he told RTS.