The driver of the bus, Ertugrul Karasu, lost control around 2:30 a.m., local time, near the Olukkaya neighborhood in the Pinarbasi district, Cihan news agency reported.
The bus veered off the snow-covered highway and tipped onto its side after striking the road barrier. The bus tumbled several times before sliding into a ditch, the Hurriyet Daily News reported.
Police said fog and icy road conditions may have triggered the crash but are also investigating whether the driver fell asleep at the wheel.
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