A bus carrying tourists from the Italian town of Monteriggioni and Badesse plunged off the highway and flipped over on Wednesday, May 22.
Citizens of Armenia, Russia, Georgia and Kazakhstan were among the 60 travelers inside the bus that overturned not far from Siena.
A 40-year-old-woman was killed, 19 other passengers were injured, Vesti.ru reports.
The woman in the front seat, who is allegedly the guide, flew through the window, after which the bus flipped and crashed onto her. The rescuers discovered her body only after lifting the bus with a crane.
While the cause of the accident has yet to be revealed, the bus driver has been tested for alcohol, but the results have not been made public.
It is possible that the man could fall asleep at the wheel or lost control on a wet road after a rain.