TAIPEI, Taiwan — The driver of a Taiwanese tour bus that crashed and burst into flames killing all 26 on board, including 23 Chinese tourists, was driving drunk, investigators said Friday.

Police coroners in Taoyuan county south of Taipei said they tested the driver’s blood, urine and stomach contents and found all registered for alcohol concentrations above the legal limit.

“Since clarifying the whereabouts of the driver before his death, (he was found to have) imbibed alcohol and was determined to have been driving drunk,” chief Taoyuan investigator Wang Yi-wen told reporters.

The announcement adds to impressions that safety lapses led to the crash and the high loss of life. Investigators said earlier they had found traces of gasoline in the driver’s compartment and the luggage hold, raising the possibility that fuel was being stored on the bus for some reason. A safety exit was also found to have been locked, trapping those on board.

Despite that, investigators still haven’t said what caused the bus to start emitting smoke before smashing into the guardrail in the July 19 disaster.

Including a Chinese tour guide, 24 of those on board were visitors from northeast China’s Liaoning province who had been scheduled to fly home on the afternoon of the accident, which took place on the highway near Taiwan’s main international airport. The others killed were the driver and a tour guide, both Taiwanese.

The disaster was the deadliest single incident involving Chinese tourists since Taiwan began admitting to the self-governing island in 2008.