Taiwanese investigators say the driver of a tour bus that crashed and burst into flames killing all 26 on board was driving drunk.

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

Friday's announcement adds to impressions that safety lapses led to the crash and the high loss of life. Among the dead were 23 Chinese tourists.

Investigators said earlier they had found traces of gasoline in the driver's compartment and the luggage hold, while a safety exit was 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.