Taipei – The deadly bus crash in Taiwan that killed an entire Chinese tour group was caused by a “suicidal” driver who intentionally set the vehicle on fire, investigators said Saturday.

Authorities had earlier said the driver Su Ming-cheng had been drunk when his bus caught fire and rammed through an expressway in July, killing himself and 25 others on board.

Minutes before the incident, Su – who was driving the group to the airport – poured gasoline over the driver’s seat and on the floor near the exit before sparking the fire with a lighter, investigators said.

“(Su), who was drunk driving, committed suicide by pouring gasoline and setting a fire, killing other passengers,” local prosecutors said in a statement Saturday.

The probe uncovered dozens of phone records between Su and his family in the days before the crash, with relatives pleading for him not to commit suicide.

“Don’t you love the three children in your family? Don’t let them be ashamed. If you do this, it will bring shame to us all,” a text message from his sister read.

The Taiwanese driver was also described by authorities as a regular drinker with a violent history.

Su had been hit with separate lawsuits for scuffling with a tour guide and sexually assaulting an unnamed victim. In both cases, investigators said he was intoxicated.

“Because of this, Su was depressed,” prosecutors said.

In May, Su was briefly suspended by his employer for fighting with another tour guide.

Su’s job driving the group from China’s northeast city Dalian in July was his first after the suspension, according to officials.

The incident prompted Chinese authorities to demand the island take measures to improve safety for mainland visitors.

Taiwan saw a boom in tourism from China under previous president Ma Ying-jeou, who oversaw an unprecedented eight-year rapprochement with Beijing.

But numbers have slipped since Beijing-sceptic Tsai Ing-wen won a landslide victory in elections in January, with the number of mainland tourists dropping by almost 24 per cent from May 20 to Sept 6.